Polyester process using a pipe reactor

ABSTRACT

The invention is directed to polyester processes that utilizes a pipe reactor in the esterification, polycondensation, or both esterification and polycondensation processes. Pipe reactor processes of the present invention have a multitude of advantages over prior art processes including improved heat transfer, volume control, agitation and disengagement functions.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of 10/919,931 filed Aug. 17, 2004 nowU.S. Pat. No. 7,345,139 which is a continuation of 10/456,212 filed Jun.6, 2003 now U.S. Pat. No. 6,906,164 which is a Continuation-in-Part of10/013,318 filed Dec. 7, 2001 now U.S. Pat. No. 6,861,494 which claimsbenefit of 60/254,040 filed Dec. 7, 2000. The above-referencedapplications and patents are incorporated by reference herein.

BACKGROUND OF THE INVENTION Field of the Invention

This invention relates generally to polyester processes and apparatuses,wherein the esterification, polycondensation, or both esterification andpolycondensation process is performed in a pipe reactor.

As the business of manufacturing polyesters becomes more competitive,alternative manufacturing processes have become highly desirable. Avariety of processes haye been developed. Early efforts used reactivedistillation (U.S. Pat. No. 2,905,707) with ethylene glycol (“EG”) vaporas reactants (U.S. Pat. No. 2,829,153). Multiple stirred pots have beendisclosed to gain additional control of the reaction (U.S. Pat. No.4,110,316 and WO 98/10007). U.S. Pat. No. 3,054,776 discloses the use oflower pressure drops between reactors, while U.S. Pat. No. 3,385,881discloses multiple reactor stages within one reactor shell. Thesedesigns were improved to solve problems with entrainment or plugging,heat integration, heat transfer, reaction time, the number of reactors,etc., as described in U.S. Pat. Nos. 3,118,843; 3,582,244; 3,600,137;3,644,096; 3,689,461; 3,819,585; 4,235,844; 4,230,818; and 4,289,895.Unfortunately, these reactors and plants are extremely complex. Forexample, the stirred polycondensation reactors have complex designs,which require detailed calculations and craftsmanship. The reactor mustoperate under a vacuum and, whether heated or cooled, maintain its shapeso the agitator does not scrape the walls, and a close tolerance ismaintained to provide effective mass transfer. Such complex designscannot be built or installed quickly and require expertise to maintainand operate.

Conventional cylindrical esterification or ester exchange reactors, suchas a continuous stirred tank reactor (“CSTR”) have many internals, suchas baffles, pipe coils for heating, large overflow weirs, trays,packing, agitators, and draft tubes, etc. Esterification or esterexchange reactors can also be reactive distillation, stripper, orrectification columns with their associated internal trays, packing,downcomers, reboilers, condensers, internal heat exchangers, refluxsystems, pumps, etc. Conventional polycondensation reactors, which aretypically a psuedo, plug flow device, which tries to maintain an averageresidence time with a narrow time distribution, are typically a (1)CSTR, typically of the wipe film or thin film reactor type, or (2)reactive distillation device. Such conventional condensation reactorscommonly have a means of enhancing the surface renewal, usually bymaking thin films of the polymer. Such conventional polycondensationdevices contain trays, internal heating coils, weirs, baffles, wipefilms, internal agitators, and large agitators with seals or magneticdrives, etc. These reactors normally have scrapers or other highlycomplicated devices for keeping the vapor lines from plugging. Manypolycondensation reactors also have very tight tolerance requirementsand must maintain their shape over a range of temperatures. Thesecylindrical reactors require a large amount of engineering, drafting,and skilled craftsmanship to construct. The cylindrical reactor also hasa specially fabricated jacket having multiple partial pipe jackets andweld lines connecting the pipe jackets to each other and the reactor.The cylindrical reactor has additional external components such asgearboxes, agitators, seal systems, motors, and the like. The extracomplexity, materials, and skill required to construct the cylindricalreactors leads to the higher cost.

A pipe has been disclosed in prior art patents that is integrated intothe process or equipment. U.S. Pat. No. 3,192,184, for example,discloses an internally baffled pipe within the reactor, and U.S. Pat.No. 3,644,483 discloses the use of a pipe for paste addition. As otherexamples, Patent Application WO 96/22318 and U.S. Pat. No. 5,811,496disclose two pipe reactors between the esterification and polymerizationreactors, and U.S. Pat. No. 5,786,443 discloses a pipe reactor betweenan esterification reactor and a heater leading to a staged reactor. Eachof these reactor trains incorporates a pipe reactor into the othercomplex reactors and equipment.

While it has been theorized that optimum ester exchange oresterification would occur in a continuum of continuous pressurereduction and continuous temperature increase (see FIG. 1, Santosh K.Gupta and Anil Kumar, Reaction Engineering of Step GrowthPolymerization, The Plenum Chemical Engineering Series, Chapter 8,Plenum Press, 1987), the cost of doing so with existing conventionalequipment is prohibitive, because it requires numerous small reactors,each with their own associated instruments and valves for level,pressure, and temperature control and pumps. Thus, in conventionalpolyester plant designs the number of pressure reduction stages(cylindrical reactors) is minimized to minimize cost. The tradeoff isthat if the number of reactors were instead increased, then the pressuredrop would be minimized.

There is a need in the art for simpler apparatuses and processes formaking polyesters.

SUMMARY OF THE INVENTION

The present invention relates to equipment and processes for themanufacture of polyesters. More specifically, the present inventionrelates to pipe reactors and associated equipment and processes for usein both new and existing (retrofitted) polyester plants. The startingmaterials, or the reactants, can be liquid, gas, or solid feedstocksusing any components for the polyester or modifiers. The present pipereactor invention has many advantages over conventional polyesterprocesses and apparatuses.

This pipe reactor process of the present invention allows the designerto decouple from each other the reactor heat transfer, volume (i.e.residence time), agitation, and disengagement functions. With respect toheat transfer, the pipe reactors of the present invention do not requireinternal heating coils of a continuous stirred tank reactor, but insteadcan use various heating means such as a heat exchanger or jacketed pipe.Among many limitations of CSTRs, the amount of heating coils is limiteddue to the need to maintain agitation of the fluids. Too many heatingcoils do not allow enough space between coils for agitation. Because theheat transfer function and agitation function are decoupled in a pipereactor system, this limitation of CSTRs, among others, is not presentin the pipe reactor system of the present invention.

Pipe reactors are not limited to the volume of a vessel for kineticconsiderations as is the case with a CSTR; pipe reactors utilize thelength of pipe for kinetics, which can be varied in a simple manner. Asto mass transfer or agitation, pipe reactors do not require a propelleror impeller of a CSTR; instead, a pump or gravity flow can be used tomove fluid around.

With respect to disengagement, which is the separation of the gas fromthe liquid interface, a CSTR process controls the liquid/gas interfaceby reactor volume. Controlling the interface by controlling the reactivevolume is a difficult way to control the velocity of the fluids. If theCSTR is made tall and skinny, the level control becomes difficult,agitator shaft deflections and seal problems increase, vapor velocitiesincrease with increased entrainment, and reactor costs increase with theincreased surface area. On the other hand, if the CSTR is made short andfat, not enough heating coils can be introduced into the reactor,agitation is more difficult with the larger diameter, and for largescale plants, shipping the vessel becomes an issue. Thus, there areoptimum dimensions for the length, width and height of a CSTR, whichthereby makes it difficult to modify the CSTR to control to the velocityof the fluids. As such, in a CSTR operation, more vapor removaloperations are required to control the vapor velocity. However,additional vapor removal operations lead to the problems of entrainedliquid being removed by the vapor and loss of yield. Conversely, in apipe reactor system of the invention herein, to control the liquid/gasinterface, additional pipes (pipe reactors) in parallel can be added tocontrol the total fluid velocity and gas velocity leaving the surface.Thus, with a pipe reactor system of the present invention, thedisengagement functions are simpler and much easier to control than thatof a conventional CSTR system. Similar disadvantages can be found inother conventional reactor systems for making polyesters found in theart, such as reactive distillation, stripper, or rectification columns,or tank with internals, screw, or kneader reactors in comparison to theabove stated advantages of the pipe reactor design of the presentinvention.

Surprisingly, the pipe reactors of the present invention can be used forpolyester processes, which typically have long residence times.Generally, pipe reactors are used for processes having only very shortresidence times. However, it has been found herein that the pipereactors of the present invention can be used for longer residence timepolyester production processes.

Accordingly, in one embodiment, the invention is directed to a processfor making a polyester polymer from a plurality of reactants,comprising:

-   -   a. providing an esterification pipe reactor having an inlet, an        outlet, and an interior surface, the esterification pipe reactor        comprising a substantially empty pipe;    -   b. adding at least one reactant into the pipe reactor proximal        the inlet so that the reactants flow through the pipe reactor        and react with each other to form a polyester monomer within the        pipe reactor and the polyester monomer exits from the outlet        thereof, wherein the reactants and the polyester monomer flowing        through the esterification pipe reactor are each an        esterification fluid;    -   c. providing a polycondensation pipe reactor formed separately        of the esterification pipe reactor, the polycondensation pipe        reactor in fluid communication with the esterification pipe        reactor, the polycondensation pipe reactor having a first end, a        second end, and an inside surface, the polycondensation pipe        reactor comprising a substantially empty pipe; and    -   d. directing the fluid polyester monomer into the first end of        the polycondensation pipe reactor so that the monomer flows        through the polycondensation reactor, the monomer reacting to        form an oligomer and then the oligomer reacting to form the        polymer within the polycondensation pipe reactor, and the        polymer exits from the second end of the reactor, wherein the        monomer, the oligomer, and the polymer flowing through the        polycondensation pipe reactor are each a polycondensation fluid.

In another embodiment, the invention is directed to a process for makinga polyester polymer from a plurality of reactants, comprising:

-   -   a. providing an esterification pipe reactor having an inlet, an        outlet, and an interior surface;    -   b. adding at least one reactant into the pipe reactor proximal        the inlet so that the reactants flow through the pipe reactor        and react with each other to form a polyester monomer within the        pipe reactor and the polyester monomer exits from the outlet        thereof, wherein the reactants and the polyester monomer flowing        through the esterification pipe reactor are each an        esterification fluid, wherein the reactants comprise        terephthalic acid or dimethylterephthalate;    -   c. providing a polycondensation pipe reactor formed separately        of the esterification pipe reactor, the polycondensation pipe        reactor in fluid communication with the esterification pipe        reactor, the polycondensation pipe reactor having a first end, a        second end, and an inside surface; and    -   d. directing the fluid polyester monomer into the first end of        the polycondensation pipe reactor so that the monomer flows        through the polycondensation reactor, the monomer reacting to        form an oligomer and then the oligomer reacting to form the        polymer within the polycondensation pipe reactor, and the        polymer exits from the second end of the reactor, wherein the        monomer, the oligomer, and the polymer flowing through the        polycondensation pipe reactor are each a polycondensation fluid.

In another embodiment, the invention is directed to a process for makinga polyester polymer from a plurality of reactants, comprising:

-   -   a. providing an esterification pipe reactor having an inlet, an        outlet, and an interior surface;    -   b. adding at least one reactant into the pipe reactor proximal        the inlet so that the reactants flow through the pipe reactor        and react with each other to form a polyester monomer within the        pipe reactor and the polyester monomer exits from the outlet        thereof, wherein the reactants and the polyester monomer flowing        through the esterification pipe reactor are each an        esterification fluid;    -   c. providing a polycondensation pipe reactor formed separately        of the esterification pipe reactor, the polycondensation pipe        reactor in fluid communication with the esterification pipe        reactor, the polycondensation pipe reactor having a first end, a        second end, and an inside surface; and    -   d. directing the fluid polyester monomer into the first end of        the polycondensation pipe reactor so that the monomer flows        through the polycondensation reactor, the monomer reacting to        form an oligomer and then the oligomer reacting to form the        polymer within the polycondensation pipe reactor, and the        polymer exits from the second end of the reactor, wherein the        monomer, the oligomer, and the polymer flowing through the        polycondensation pipe reactor are each a polycondensation fluid.

In another embodiment, the invention is directed to a process for makinga polyester polymer from a plurality of reactants, comprising:

-   -   a. providing a combined esterification and prepolymer        polycondensation pipe reactor having an inlet, an outlet, and an        interior surface;    -   b. adding at least one reactant into the pipe reactor proximal        the inlet so that the reactants flow through the pipe reactor        and react with each other to form a polyester oligomer within        the pipe reactor and the polyester oligomer exits from the        outlet thereof, wherein the reactants and the polyester oligomer        flowing through the esterification pipe reactor are each an        esterification fluid;    -   c. providing a polycondensation pipe reactor formed separately        of the combined esterification prepolymer pipe reactor, the        polycondensation pipe reactor in fluid communication with the        esterification/prepolymer pipe reactor, the polycondensation        pipe reactor having a first end, a second end, and an inside        surface; and    -   d. directing the fluid polyester oligomer into the first end of        the polycondensation pipe reactor so that the oligomer flows        through the polycondensation reactor, the oligomer reacting to        form the polymer within the polycondensation pipe reactor, and        the polymer exits from the second end of the reactor, wherein        the oligomer and the polymer flowing through the        polycondensation pipe reactor are each a polycondensation fluid.

In another embodiment, the invention is directed to a process for makinga polyester polymer from a plurality of reactants, comprising:

-   -   a. providing an esterification pipe reactor having an inlet, an        outlet, and an interior surface;    -   b. adding at least one reactant into the pipe reactor proximal        the inlet so that the reactants flow through the pipe reactor        and react with each other to form a polyester monomer within the        pipe reactor and the polyester monomer exits from the outlet        thereof, wherein the reactants and the polyester monomer flowing        through the esterification pipe reactor are each an        esterification fluid;    -   c. providing a polycondensation pipe reactor integrally combined        with the esterification pipe reactor, the polycondensation pipe        reactor in fluid communication with the esterification pipe        reactor, the polycondensation pipe reactor having a first end, a        second end, and an inside surface; and    -   d. directing the fluid polyester monomer into the first end of        the polycondensation pipe reactor so that the monomer flows        through the polycondensation reactor, the monomer reacting to        form an oligomer and then the oligomer reacting to form the        polymer within the polycondensation pipe reactor, and the        polymer exits from the second end of the reactor, wherein the        monomer, the oligomer, and the polymer flowing through the        polycondensation pipe reactor are each a polycondensation fluid.

In another embodiment, the invention is directed to a process for makinga polyester oligomer from a plurality of reactants, comprising:

-   -   a. providing an esterification pipe reactor having an inlet, an        outlet, and an interior surface;    -   b. adding at least one reactant into the pipe reactor proximal        the inlet so that the reactants flow through the pipe reactor        and react with each other to form a polyester monomer within the        pipe reactor and the polyester monomer exits from the outlet        thereof, wherein the reactants and the polyester monomer flowing        through the esterification pipe reactor are each an        esterification fluid;    -   c. providing a prepolymer polycondensation pipe reactor formed        separately of the esterification pipe reactor, the        polycondensation pipe reactor in fluid communication with the        esterification pipe reactor, the polycondensation pipe reactor        having a first end, a second end, and an inside surface; and    -   d. directing the fluid polyester monomer into the first end of        the polycondensation pipe reactor so that the monomer flows        through the polycondensation reactor, the monomer reacting to        form the oligomer within the polycondensation pipe reactor, and        the oligomer exits from the second end of the reactor, wherein        the monomer and the oligomer flowing through the        polycondensation pipe reactor are each a polycondensation fluid.

In another embodiment, the invention is directed to a process for makinga polyester oligomer from a plurality of reactants, comprising:

-   -   a. providing an esterification pipe reactor having an inlet, an        outlet, and an interior surface;    -   b. adding at least one reactant into the pipe reactor proximal        the inlet so that the reactants flow through the pipe reactor        and react with each other to form a polyester monomer within the        pipe reactor and the polyester monomer exits from the outlet        thereof, wherein the reactants and the polyester monomer flowing        through the esterification pipe reactor are each an        esterification fluid;    -   c. providing a prepolymer polycondensation pipe reactor        integrally combined with the esterification pipe reactor, the        polycondensation pipe reactor in fluid communication with the        esterification pipe reactor, the polycondensation pipe reactor        having a first end, a second end, and an inside surface; and    -   d. directing the fluid polyester monomer into the first end of        the polycondensation pipe reactor so that the monomer flows        through the polycondensation reactor, the monomer reacting to        form the oligomer within the polycondensation pipe reactor, and        the oligomer exits from the second end of the reactor, wherein        the monomer and the oligomer flowing through the        polycondensation pipe reactor are each a polycondensation fluid.

In another embodiment, the invention is directed to a process for makinga polyester monomer from a plurality of reactants, comprising:

-   -   a. providing an esterification pipe reactor having an inlet, an        outlet, an interior surface, and at least one weir attached to        the interior surface thereof; and    -   b. adding at least one reactant into the pipe reactor proximal        the inlet so that the reactants flow through the pipe reactor,        the reactants reacting with each other to form the polyester        monomer within the pipe reactor and the polyester monomer exits        from the outlet thereof, wherein the reactants and the polyester        monomer flowing through the esterification pipe reactor are each        an esterification fluid, and wherein the esterification fluids        flow over the weir.

In another embodiment, the invention is directed to a process for makinga polyester monomer from a plurality of reactants, comprising:

-   -   a. providing an esterification pipe reactor having an inlet, an        outlet, and an interior surface;    -   b. adding at least one reactant into the pipe reactor proximal        the inlet so that the reactants flow through the pipe reactor,        the reactants reacting with each other to form the polyester        monomer within the pipe reactor and the polyester monomer exits        from the outlet thereof, and wherein the reactants and the        polyester monomer flowing through the esterification pipe        reactor are each an esterification fluid; and    -   c. recirculating a portion of the process fluids and directing        the recirculation effluent back to and therethrough the        esterification reactor proximate the inlet of the esterification        reactor or between the inlet and outlet of the esterification        reactor.

In another embodiment, the invention is directed to a process for makinga polyester monomer from a plurality of reactants, comprising:

-   -   a. providing an esterification pipe reactor having an inlet, an        outlet, and an interior surface;    -   b. adding at least one reactant into the pipe reactor proximal        the inlet so that the reactants flow through the pipe reactor,        the reactants reacting with each other to form the polyester        monomer within the pipe reactor and the polyester monomer exits        from the outlet thereof, wherein the reactants and the polyester        monomer flowing through the esterification pipe reactor are each        an esterification fluid; and    -   c. removing vapors from the pipe reactor intermediate its inlet        and its outlet and/or proximate its outlet through a vent of        empty pipe.

In another embodiment, the invention is directed to a process for makinga polyester monomer from a plurality of reactants, comprising:

-   -   a. providing an esterification pipe reactor having an inlet, an        outlet, and an interior surface, the inlet being positioned at        least 20 vertical feet below the outlet;    -   b. adding at least one reactant into the pipe reactor proximal        the inlet so that the reactants flow through the pipe reactor,        the reactants reacting with each other to form the polyester        monomer within the pipe reactor and the polyester monomer exits        from the outlet thereof, and wherein the reactants and the        polyester monomer flowing through the esterification pipe        reactor are each an esterification fluid.

In another embodiment, the invention is directed to a process for makinga polyester monomer from a plurality of reactants, comprising:

-   -   a. providing an esterification pipe reactor having an inlet, an        outlet, and an interior surface;    -   b. adding at least one reactant into the pipe reactor proximal        the inlet so that the reactants flow through the pipe reactor,        the reactants reacting with each other to form the polyester        monomer within the pipe reactor and the polyester monomer exits        from the outlet thereof, wherein the reactants and the polyester        monomer flowing through the esterification pipe reactor are each        an esterification fluid, and wherein the fluids present in the        pipe reactor are in a bubble or froth flow regime.

In another embodiment, the invention is directed to a process for makinga polyester monomer from a plurality of reactants, comprising:

-   -   a. providing an esterification pipe reactor having an inlet, an        outlet, and an interior surface, wherein the pipe reactor has        alternating linear and non-linear sections extending in its        lengthwise direction between the inlet and outlet thereof;    -   b. adding at least one reactant into the pipe reactor proximal        the inlet so that the reactants flow through the pipe reactor,        the reactants reacting with each other to form the polyester        monomer within the pipe reactor and the polyester monomer exits        from the outlet thereof, wherein the reactants and the polyester        monomer flowing through the esterification pipe reactor are each        an esterification fluid.

In another embodiment, the invention is directed to a process for makinga polyester monomer from a plurality of reactants, comprising:

-   -   a. providing an esterification pipe reactor having an inlet, an        outlet, and an interior surface; and    -   b. adding at least one reactant into the pipe reactor proximal        the inlet so that the reactants flow through the pipe reactor,        the reactants reacting with each other to form the polyester        monomer within the pipe reactor and the polyester monomer exits        from the outlet thereof, wherein the at least one reactant and        the polyester monomer flowing through the esterification pipe        reactor are each an esterification fluid.

In another embodiment, the invention is directed to a process for makinga polyester polymer, comprising:

-   -   a. providing a polycondensation pipe reactor having a first end,        a second end, and an inside surface, the first end being        disposed vertically above the second end, the polycondensation        pipe reactor having alternating linear and non-linear sections        extending in its lengthwise direction between its first end and        its second end; and    -   b. directing a fluid polyester monomer into the first end of the        polycondensation pipe reactor so that the monomer flows through        the polycondensation reactor, the monomer reacting to form an        oligomer and then the oligomer reacting to form the polymer        within the polycondensation pipe reactor, and the polymer exits        from the second end of the reactor, wherein the monomer, the        oligomer, and the polymer flowing through the polycondensation        pipe reactor are each a polycondensation fluid.

In another embodiment, the invention is directed to a process for makinga polyester polymer, comprising:

-   -   a. providing a polycondensation pipe reactor having a first end,        a second end, an inside surface, and at least one weir attached        to the inside surface thereof, wherein the pipe reactor is made        of a substantially empty pipe; and    -   b. directing a fluid polyester monomer into the first end of the        polycondensation pipe reactor so that the monomer flows through        the polycondensation reactor, the monomer reacting to form an        oligomer and then the oligomer reacting to form the polymer        within the polycondensation pipe reactor, and the polymer exits        from the second end of the reactor, wherein the monomer, the        oligomer, and the polymer flowing through the polycondensation        pipe reactor are each a polycondensation fluid, and wherein at        least one of the polycondensation fluids flows over the weir.

In another embodiment, the invention is directed to a process for makinga polyester polymer, comprising:

-   -   a. providing a polycondensation pipe reactor having a first end,        a second end, and an inside surface; and    -   b. directing a fluid polyester monomer into the first end of the        polycondensation pipe reactor so that the monomer flows through        the polycondensation reactor, the monomer reacting to form an        oligomer and then the oligomer reacting to form the polymer        within the polycondensation pipe reactor, and the polymer exits        from the second end of the reactor, wherein the monomer, the        oligomer, and the polymer flowing through the polycondensation        pipe reactor are each a polycondensation fluid; and    -   c. removing vapors from the pipe reactor intermediate its inlet        and its outlet and/or proximate its inlet or outlet through a        vent comprising substantially empty pipe.

In another embodiment, the invention is directed to a process for makinga polyester polymer, comprising:

-   -   a. providing a polycondensation pipe reactor having a first end,        a second end, and an inside surface; and    -   b. directing a fluid polyester monomer into the first end of the        polycondensation pipe reactor so that the monomer flows through        the polycondensation reactor, the monomer reacting to form an        oligomer and then the oligomer reacting to form the polymer        within the polycondensation pipe reactor, and the polymer exits        from the second end of the reactor, wherein the monomer, the        oligomer, and the polymer flowing through the polycondensation        pipe reactor are each a polycondensation fluid, and wherein the        fluids present in the pipe reactor are in a stratified flow        regime.

In another embodiment, the invention is directed to a a process formaking a polyester polymer, comprising:

-   -   a. providing a polycondensation pipe reactor having a first end,        a second end, and an inside surface; and    -   b. directing a fluid polyester monomer into the first end of the        polycondensation pipe reactor so that the monomer flows through        the polycondensation reactor, the monomer reacts to form an        oligomer and then the oligomer reacts to form the polymer within        the polycondensation pipe reactor, and the polymer exits from        the second end of the reactor, wherein the monomer, the        oligomer, and the polymer flowing through the polycondensation        pipe reactor are each a polycondensation fluid.

In another embodiment, the invention is directed to a process for makinga polyester polymer, comprising:

-   -   a. providing a polycondensation pipe reactor having a first end,        a second end, and an inside surface; and    -   b. directing a fluid polyester oligomer into the first end of        the polycondensation pipe reactor so that the oligomer flows        through the polycondensation pipe reactor, the oligomer reacting        to form the polyester polymer within the polycondensation pipe        reactor and the polyester polymer exits from the second end        thereof.

In another embodiment, the invention is directed to an apparatus forproducing a polyester polymer, comprising:

-   -   a. an esterification pipe reactor having an inlet, an outlet,        and an interior surface through which esterification fluid        reactants are passed; and    -   b. a polycondensation pipe reactor formed separately of and in        fluid communication with the esterification reactor, wherein the        polycondensation reactor has an inlet, an outlet, and an        interior surface through which at least one polycondensation        fluid reactant is passed, wherein the esterification and        polycondensation reactors comprise substantially empty pipe.

In another embodiment, the invention is directed to an apparatus forproducing a polyester polymer, comprising:

-   -   a. an esterification pipe reactor having an inlet, an outlet,        and an interior surface through which esterification fluid        reactants are passed; and    -   b. a polycondensation pipe reactor formed separately of and in        fluid communication with the esterification reactor,    -   wherein the polycondensation reactor has an inlet, an outlet,        and an interior surface through which at least one        polycondensation fluid reactant is passed.

In another embodiment, the invention is directed to an esterificationpipe reactor apparatus for producing a polyester monomer, comprising:

-   -   a. an esterification pipe reactor having an inlet, an outlet,        and an interior surface; and    -   b. a recirculation loop having an influent and an effluent, the        effluent being in fluid communication with the esterification        pipe reactor.

In another embodiment, the invention is directed to an apparatus forproducing a polyester monomer, oligomer, or polymer, comprising:

-   -   a. a pipe reactor having an inlet, an outlet, and an interior        surface through which the fluid reactants are passed; and    -   b. a weir connected to a portion of the interior surface of the        pipe reactor and adjacent the outlet thereof,    -   wherein the reactor comprises substantially empty pipe.

In another embodiment, the invention is directed to an apparatus forproducing a polyester monomer, oligomer, or polymer, comprising:

-   -   a. a pipe reactor having an inlet, an outlet, and an interior        surface through which the fluid reactants are passed; and    -   b. a vent in fluid communication with the reactor, the vent        further comprising an upstanding degas stand pipe coupled to the        vent, the degas stand pipe having a receiving end in fluid        communication with the vent and an opposed venting end disposed        vertically above the receiving end, and wherein the degas stand        pipe is non-linear extending in its lengthwise direction between        the receiving end and the venting end thereof, and wherein the        degas stand pipe is formed of three contiguous sections each in        fluid communication with each other, a first section adjacent        the receiving end and extending substantially vertically from        the vent, a second section coupled to the first section and        oriented at an angle relative to the first section in plan view,        and a third section coupled to the second section and oriented        at a complimentary angle relative to the second section in plan        view so that the third section is oriented substantially        horizontally.

In another embodiment, the invention is directed to an apparatus forproducing a polyester monomer, oligomer, or polymer comprising:

-   -   a. a pipe reactor having an inlet, an outlet, and an interior        surface through which the fluid reactants are passed.

In another embodiment, the invention is directed to an apparatus forventing a process of gas or vapor while effectively disengaging liquidfrom the gas or vapor, the liquid, gas, and vapor being fluids,separating the liquid from the gas or vapor, and returning the liquidback to the process, comprising:

-   -   a. a vessel or process pipe containing (i) liquid and (ii) gas        or vapor; and    -   b. a vent in fluid communication with the vessel or process        pipe, the vent further comprising an upstanding degas stand pipe        coupled to the vent, the degas stand pipe having a receiving end        in fluid communication with the vent and an opposed venting end        disposed vertically above the receiving end, and wherein the        degas stand pipe is non-linear extending in its lengthwise        direction between the receiving end and the venting end thereof,        and wherein the degas stand pipe is formed of three contiguous        sections each in fluid communication with each other, a first        section adjacent the receiving end and extending substantially        vertically from the vent, a second section coupled to the first        section and oriented at an angle relative to the first section        in plan view, and a third section coupled to the second section        and oriented at an angle relative to the second section in plan        view so that the third section is oriented substantially        horizontally.

In another embodiment, the invention is directed to a fluid mixing anddistribution system adapted for the mixture, storage, and distributionof fluids to a separate plant process distribution system, comprising:

-   -   a. a first elongate and vertically disposed fluid storage        vessel;    -   b. a circulating pump in fluid communication with the first        vessel and the second vessel, the circulating pump being        constructed and arranged to pass a fluid flow through the system        and to circulate the fluid from the first vessel into the second        vessel and from the first vessel to the first vessel;    -   c. a second fluid storage and dispensing vessel in fluid        communication with the first vessel and the second vessel being        disposed at a greater vertical elevation than the first vessel;        and    -   d. a control valve in fluid communication with the circulating        pump, the first vessel and the second vessel, respectively, the        control valve being constructed and arranged to selectively        direct the fluid flow from the first vessel into the second        vessel and from the first vessel into the first vessel,    -   wherein the second vessel is in fluid communication with the        plant process distribution system, and wherein a static pressure        head formed by the fluid held within the second vessel is used        to pass the fluid from the second vessel to the plant process        distribution system.

In another embodiment, the invention is directed to a fluid mixing anddistribution system adapted for the mixture, storage, and distributionof fluids to a separate plant process distribution system, comprising:

-   -   a. a first fluid storage vessel;    -   b. a second fluid mixing and storage vessel;    -   c. a circulating pump in fluid communication with the first        vessel and the second vessel, the circulating pump being        constructed and arranged to circulate the fluid through the        system and from the first vessel into the second vessel;    -   d. the second vessel being disposed at a greater vertical        elevation than both of the first vessel and the plant process        distribution system; and    -   e. a control valve in fluid communication with the circulating        pump, the first vessel and the second vessel, respectively, the        control valve being constructed and arranged to selectively        direct the fluid flow from the first vessel back into the first        vessel and from the first vessel into the second vessel;    -   f. the second vessel being in fluid communication with the plant        process distribution system, wherein a static pressure head        formed by the fluid held within the second vessel is used to        pass the fluid from the second vessel to the plant process        distribution system.

In another embodiment, the invention is directed to a method of mixingand distribution a fluid within a fluid mixing and distribution systemadapted for the mixture, storage, and distribution of fluids to aseparate plant process distribution system, comprising:

-   -   a. placing at least one fluid into a first elongate and        vertically disposed fluid storage vessel;    -   b. passing the fluid from the first vessel into a second        elongate and vertically disposed fluid mixing and storage        vessel, the second fluid vessel being disposed at a greater        vertical elevation than both of the first vessel and the plant        process distribution system, with a circulating pump in fluid        communication with the first vessel and the second vessel, the        circulating pump being constructed and arranged to pass the        fluid through the system;    -   c. using a control valve in fluid communication with the        circulating pump, the first vessel and the second vessel to        selectively direct the fluid from the first vessel to either of        the first vessel and the second vessel; and    -   d. selectively passing the fluid from the second vessel to the        plant process distribution system, the second vessel creating a        static pressure head used to pass the fluid stored therein to        the plant process distribution system.

In another embodiment, the invention is directed to a heat transfermedia control system for use with a pipe reactor system, the pipereactor system having a supply heat transfer media loop through which afirst stream of a heat transfer media is passed and a return heattransfer media loop through which a second stream of the heat transfermedia is passed, the temperature of the first heat transfer media streambeing greater than the temperature of the second heat transfer mediastream, said heat transfer media control system comprising:

-   -   a. a first heat transfer media header through which the first        heat transfer media stream is passed;    -   b. a second heat transfer media header through which the second        heat transfer media stream is passed;    -   c. a first heat transfer media sub-loop, through which the heat        transfer media may be passed, from the first to the second        headers, respectively;    -   d. a control valve in fluid communication with a selected one of        the headers and the first sub-loop;    -   e. the pressure of the first heat transfer media stream within        the first header being greater than the pressure of the second        heat transfer media stream within the second header;    -   f. wherein the control valve is used to selectively direct at        least a portion of the first heat transfer media stream into the        first sub-loop using the pressure of the first heat transfer        media stream to pass the heat transfer media, and to also        control the temperature and pressure of the heat transfer media        stream being passed through the first sub-loop.

In another embodiment, the invention is directed to a heat transfermedia control system for use with a pipe reactor system, the pipereactor system having a supply heat transfer media loop through which afirst stream of a heat transfer media is passed and a return heattransfer media loop through which a second stream of the heat transfermedia is passed, the temperature of the first heat transfer media streambeing greater than the temperature of the second heat transfer mediastream, said heat transfer media control system comprising:

-   -   a. a first heat transfer media header through which the first        heat transfer media stream is passed;    -   b. a second heat transfer media header through which the second        heat transfer media stream is passed;    -   c. a first heat transfer media sub-loop through which the heat        transfer media may be passed from the first header to the second        header;    -   d. a first control valve in fluid communication with the first        header and the first sub-loop; and    -   e. a second control valve in fluid communication with the first        sub-loop and the second header;    -   f. the pressure of the first heat transfer media stream within        the first header being greater than the pressure of the second        heat transfer media stream within the second header;    -   g. wherein one or both of the control valves is used to        selectively direct at least a portion of the first heat transfer        media stream into the first sub-loop, using the pressure of the        first heat transfer media stream, to pass the heat transfer        media through the first sub-loop, and to also control the        temperature and pressure of the heat transfer media stream being        passed through the first sub-loop.

In another embodiment, the invention is directed to a method of passinga heat transfer media through a heat transfer media system for use witha pipe reactor system, the pipe reactor system having a supply heattransfer media loop through which a first stream of a heat transfermedia is passed and a return heat transfer media loop through which asecond stream of the heat transfer media is passed, the temperature andthe pressure of the first heat transfer media stream being greater thanthe temperature and the pressure of the second heat transfer mediastream, said heat transfer media control system comprising:

-   -   a. passing the first heat transfer media stream through a first        heat transfer media header;    -   b. passing the second heat transfer media stream through a        second heat transfer media header;    -   c. passing the heat transfer media from the first header through        a first heat transfer media sub-loop, in the absence of a heat        transfer media circulating pump, with a first control valve in        fluid communication with the first header and the first        sub-loop; and    -   d. passing the heat transfer media from the first sub-loop into        the second header, in the absence of a heat transfer media        circulating pump, with a second control valve in fluid        communication with the first sub-loop and the second header.

In another embodiment, the invention is directed to a fluid deliverysystem for the delivery of a process working fluid supply to a fluidprocess plant, the process plant having a pipe system for handling,distributing, and processing the fluid, the system comprising:

-   -   a. at least one delivery container positioned at a pump station;        and    -   b. at least one pump in fluid communication with the at least        one delivery container;    -   c. said at least one delivery container being in fluid        communication with a valve train, the valve train being in fluid        communication with the process plant pipe system;    -   wherein the fluid is selectively pumped directly from the at        least one delivery container through the valve train and into        the process plant pipe system in the absence of a fluid delivery        feed and storage tank for otherwise receiving and storing the        fluid from the at least one delivery container therein.

In another embodiment, the invention is directed to a fluid deliverysystem for the delivery of a process working fluid supply to a fluidprocess plant, the process plant having a pipe system for handling,distributing, and processing the fluid, the system comprising:

-   -   a. a first delivery container positioned at a pump station;    -   b. a first pump in fluid communication with the first delivery        container;    -   c. a second delivery container positioned at the pump station;        and    -   d. a second pump in fluid communication with the second delivery        container;    -   e. each of the delivery containers and pumps, respectively,        being in fluid communication with a valve train, the valve train        being comprised of a plurality of selectively operable control        valves and being in fluid communication with the process plant        pipe system;    -   wherein the fluid is selectively pumped directly from the first        and second delivery containers, respectively, through the valve        train and into the process plant pipe system in the absence of a        fluid delivery feed and storage tank.

In another embodiment, the invention is directed to a fluid deliverymethod for use in delivering a supply of a process working fluid to afluid process plant, the process plant having a pipe system forhandling, distributing, and processing the fluid, the system comprising:

-   -   a. positioning a first delivery container at a pump station, the        first delivery container being in fluid communication with a        first pump;    -   b. positioning a second delivery container at the pump station,        the second delivery container being in fluid communication with        a second pump;    -   c. selectively pumping the fluid from each of the respective        delivery containers directly into a valve train, the valve train        being comprised of a plurality of selectively operable control        valves in fluid communication with the process plant pipe        system, and through the valve train into the process plant pipe        system in the absence of a fluid delivery feed and storage tank        for otherwise receiving and storing the fluid from the at least        one delivery container therein.

In another embodiment, the invention is directed to an integrated plantwater distribution system, the water distribution system beingseparately supplied with clean, fresh water from a water supply sourcefor use within a process plant, the system comprising:

-   -   a. a safety shower water storage tank in fluid communication        with, and supplied by water from the water source;    -   b. a first water distribution loop in fluid communication with        the safety shower water storage tank and being supplied with        water therefrom;    -   c. a second water distribution loop in fluid communication with        the first water distribution loop; and    -   d. means for selectively drawing water from the first water        distribution loop to supply water to the second water        distribution loop.

In another embodiment, the invention is directed to a method ofdistributing water through an integrated plant water distributionsystem, the water distribution system being separately supplied withclean, fresh water from a water source for use within a process plant,the method comprising:

-   -   a. supplying water to a safety shower water storage tank;    -   b. passing the water from the safety shower water storage tank        into a first water distribution loop in fluid communication with        the water storage tank;    -   c. selectively passing water from the first water distribution        loop to a second water distribution loop in fluid communication        with the first water loop.

In another embodiment, the invention is directed to an integrated vacuumsystem for use with a final polycondensation reactor having separatehigh pressure, medium pressure, and low pressure polycondensation vacuumzones, respectively, the system comprising:

-   -   a. a spray condenser, said spray condenser being in fluid        communication with each of the medium and low pressure vacuum        zones, respectively, of the polycondensation reactor;    -   b. an interstage condenser in fluid communication with the spray        condenser; and    -   c. a vacuum pump in fluid communication with the interstage        condenser.

In another embodiment, the invention is directed to an integrated vacuumsystem for use with a final polycondensation reactor having at least amedium pressure polycondensation vacuum zone and a separate low pressurepolycondensation vacuum zone, the system comprising:

-   -   a. a spray condenser, said spray condenser being in fluid        communication with each of the medium and low pressure vacuum        zones, respectively, of the polycondensation reactor;    -   b. a first EG jet in fluid communication with the spray        condenser;    -   c. an interstage condenser in fluid communication with the first        EG jet;    -   d. a vacuum pump in fluid communication with the interstage        condenser; and    -   e. a second EG jet in fluid communication with the low pressure        vacuum zone and the spray condenser, respectively.

In another embodiment, the invention is directed to a method ofcollecting fluid from a final polycondensation reactor having a highpressure vacuum zone, a medium pressure vacuum zone, and a low pressurepolycondensation vacuum zone, the method comprising:

-   -   a. passing the fluid from at least the medium pressure        polycondensation vacuum zone and the low pressure        polycondensation vacuum zone of the reactor into a single spray        condenser in sealed fluid communication with each of the medium        and low pressure vacuum zones, respectively; and    -   b. drawing the fluid through an interstage condenser in fluid        communication with the spray condenser with a vacuum pump in        fluid communication with the interstage condenser.

In another embodiment, the invention is directed to a process for makinga polyester monomer, comprising:

-   -   a. providing a pipe reactor having an inlet, an outlet, and an        interior surface, the inlet disposed elevationally below the        outlet; and    -   b. adding at least one reactant into the pipe reactor proximal        the inlet so that the reactants flow through the pipe reactor,        wherein the reactants react with each other to form the        polyester monomer within the pipe reactor and the polyester        monomer exits from the outlet thereof.

In another embodiment, the invention is directed to a process for makinga polyester polymer, comprising:

-   -   a. providing a polycondensation reactor having a first end, a        second end, and an inside surface, the first end disposed        elevationally above the second end, the polycondensation reactor        being non-linear between the first end and the second end; and    -   b. directing a fluid polyester monomer into the first end of the        polycondensation reactor so that the monomer flows through the        polycondensation reactor, wherein the monomer reacts to form the        polymer within the polycondensation reactor and the polymer        exits from the second end thereof.

In another embodiment, the invention is directed to a process for makinga polyester polymer, comprising:

-   -   a. providing a polycondensation reactor having a first end, a        second end, and an inside surface, the first end disposed        elevationally above the second end, wherein the polycondensation        reactor forms an angle with a vertically-oriented plane, the        angle being greater than zero degrees; and    -   b. directing a fluid monomer into the first end of the        polycondensation reactor so that the monomer flows through of        polycondensation reactor, wherein the monomer reacts to form the        polyester polymer within the polycondensation reactor and the        polyester polymer exits from the second end thereof.

In another embodiment, the invention is directed to a process for makinga polyester, comprising:

-   -   a. providing a pipe reactor having an inlet, an outlet, and an        interior surface, the inlet disposed elevationally below the        outlet; and    -   b. adding at least one reactant into the pipe reactor proximal        the inlet so that the reactants flow through the pipe reactor,        wherein the reactants react with each other to form the        polyester within the pipe reactor and the polyester exits from        the outlet thereof.

In another embodiment, the invention is directed to an apparatus forreacting reactants into a polyester monomer, comprising:

-   -   a. a pipe reactor having an inlet, an outlet, and an interior        surface, the inlet disposed elevationally below the outlet; and    -   b. a weir connected to a portion of the interior surface of the        pipe reactor adjacent the outlet thereof.

In another embodiment, the invention is directed to an apparatus forreacting reactants into a polyester monomer, comprising:

-   -   a. a pipe reactor having an inlet, an outlet, and an interior        surface, the inlet disposed elevationally below the outlet; and    -   b. a venting mechanism incorporated into the pipe reactor so        that a fluid traversing within its interior surface also flows        through the venting mechanism when flowing from the inlet to the        outlet of the pipe reactor, the venting mechanism comprising an        eccentric flat-on-bottom reducer.

In another embodiment, the invention is directed to an apparatus forreacting reactants into a polyester monomer, comprising:

-   -   a. a pipe reactor having an inlet, an outlet, and an interior        surface, the inlet disposed elevationally below the outlet; and    -   b. a recirculation loop having an influent and an effluent, the        influent in fluid communication with the pipe reactor proximal        to its outlet and the effluent in fluid communication with the        pipe reactor adjacent its inlet

In another embodiment, the invention is directed to an apparatus forreacting a monomer into a polyester polymer, comprising:

-   -   a. a polycondensation reactor having a first end, a second end,        and an inside surface, the first end disposed elevationally        above the second end, the polycondensation reactor being formed        as a plurality of contiguous interconnected sections in which        the monomer flows along the inside surface of each section        traversing from the first end to the second end of the        polycondensation reactor, wherein adjacent sections form        non-linear angles with each other; and    -   b. at least one weir attached to the inside surface of the        polycondensation reactor, wherein one weir is located adjacent a        juncture of each of the interconnected sections

In another embodiment, the invention is directed to a process for makingan ester from a plurality of reactants comprising:

-   -   a. providing an esterification pipe reactor having a first inlet        and a first outlet;    -   b. adding the reactants under esterification reaction conditions        into the esterification pipe reactor proximate to the first        inlet and forming a two phase flow so the reactants form a        liquid phase and vapor phase through the esterification pipe        reactor and wherein at least a portion of the reactants form an        ester monomer.

In another embodiement, the invention is directed to a process formaking a polyester from a plurality of reactants comprising:

-   -   a. providing an esterification pipe reactor having a first inlet        and a first outlet;    -   b. adding the reactants under esterification reaction conditions        into the esterification pipe reactor proximate to the first        inlet and forming a two phase flow so the reactants form a        liquid phase and vapor phase flow through the esterification        pipe reactor and wherein at least a portion of the reactants        form an ester monomer;    -   c. reacting the monomer under polycondensation reaction        conditions in a polycondensation pipe reactor wherein at least a        portion of the ester monomer forms an oligomer; and    -   d. reacting the oligomer under polycondensation reaction        conditions in the polycondensation pipe reactor wherein at least        a portion of the oligomer forms a polyester.

In another embodiment, the invention is directed to an apparatus forpreparing of at least one of an ester monomer, an ester oligomer or apolyester comprising a pipe reactor having an inlet, an outlet and aninterior through which reactants of at least one of an ester monomer, anester oligomer or a polyester are passed.

The present invention provides for apparatuses for each and everyprocess embodiment, and concomitantly a process related to each andevery apparatus of the invention.

Additional advantages of the invention will be set forth in part in thedescription which follows, and in part will be obvious from thedescription, or may be easily learned by practice of the invention. Theadvantages of the invention will be realized and attained by means ofthe elements and combinations particularly pointed out in the appendedclaims. It is to be understood that both the foregoing generaldescription and the following detailed description are exemplary andexplanatory only and are not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate several embodiment(s) of theinvention and together with the description, serve to explain theprinciples of the invention.

FIG. 1 shows a typical polyester reaction temperature and pressureprofile.

FIG. 2 shows one embodiment of the esterification or thepolycondensation pipe reactor. In a polycondensation pipe reactor mode,the influent and effluent are reversed (influent at 11 and effluent at12).

FIG. 3 shows installed costs vs. nominal pipe diameter (inches) for atypical pipe reactor installed cost of this invention.

FIG. 4 shows one embodiment of the invention wherein the top of theester exchange or esterification reactor where level control occurs viaa weir into the polycondensation reactor.

FIG. 5 shows one embodiment of the invention where an existing polyesterproduction facility is modified with one or more pipe reactors.

FIG. 6 shows an embodiment of the invention where a larger plant wheremultiple parallel esterification and polycondensation pipe reactors areutilized, as well as the production of multiple products within onesystem.

FIGS. 7 a-g show various embodiments of the vapor disengagement for boththe esterification and polycondensation process.

FIG. 8 shows an embodiment of the polycondensation vapor disengagement.

FIG. 9 shows an embodiment of laminar mixing in a polycondensation zoneutilizing a weir and a reduced diameter pipe flow inverter systemdownstream of the weir.

FIG. 10 shows various embodiments of altering the esterification orester exchange reactor pressure profile using different non-linearconfigurations. This figure is presented in side view, showing thevertical displacement between each turn of the esterification or esterexchange reactor lines.

FIG. 11 is a plot of the pressure profiles corresponding to thoseconfigurations of FIG. 10.

FIGS. 12 a and 12 b show different aspects of the additive locationswithin the process.

FIGS. 13 a and 13 b show two different embodiments wherein the pastetank is eliminated by using a recirculation loop.

FIG. 14 shows an embodiment wherein the heat transfer media sublooppumps are eliminated.

FIG. 15 a shows a typical prior art mix and feed system.

FIG. 15 b shows an embodiment of the invention for the mix and feedsystem that eliminates various tanks and other control devices and unitoperations.

FIG. 16 shows an embodiment of the invention wherein an alternating lowand high pressure configuration is used for the ester exchange orpolycondensation pipe reactor.

FIGS. 17 a and b show two embodiments of the invention for a polyesterplant design integrating a pipe reactor for the esterification and apipe reactor for the polycondensation system.

FIG. 18 shows one embodiment for the polycondensation pipe reactorprocess. FIG. 8 is an exploded view of element 133 and FIG. 9 is anexploded view of element 142.

FIG. 19 is an embodiment wherein distillation is replaced withadsorption.

FIG. 20 a shows the different flow regimes of two-phase flow inhorizontal pipes.

FIG. 20 b shows the vapor mass flow vs. ratio of liquid over vapor massflow and the relationship to each flow regime of two-phase flow inhorizontal pipes from FIG. 20 a. FIG. 20 b also identifies the preferredflow regimes for esterification and polycondensation processes of thepresent invention.

FIG. 21 shows an embodiment of the invention for unloading truckswithout the use of tanks to minimize capital costs and unit operations,along with eliminating water to waste water treatment.

FIG. 22 shows an embodiment of the invention for combining safetyshower, cooling tower, cutter water and HTM pump coolers to minimize thewater systems in the facility.

FIG. 23 shows an integrated vacuum system for reducing EG jets andeliminating a chilled water system as one embodiment of the invention.

FIG. 24 shows the two-phase regimes for esterification andpolycondensation for one embodiment of a process of the presentinvention wherein a pipe reactor is used to produce PET homopolymer.

KEY TO NUMBER DESIGNATIONS IN THE DRAWINGS

DESIGNATION MEANING 10 pipe reactor 11 outlet 12 inlet 21, 22, 23, 24,25 view 31 inlet 32 fluid outlet 33 gas/vapor outlet 34 inlet 35 exit 36tee 37 eccentric flat-on-bottom reducer 38 weir 41 mix tank 42 feed tanklevel 43 pump 44 agitator 45 temperature controller 46 heat exchanger 47steam 48 water 49 feed tank 51 level 50 agitator 51 feed tank 52, 53pump 54 temperature controller 55 steam 56 water 57, 58 feed system 59feed header 60 3-way valve 71 overflow line 72 unjacketed pipe 73jacketed pipe 74 circulating pump 75 level 76 water 77 temperaturecontroller 78 steam 82 feed tank 91 recirculation loop 92 recirculationpump 93 influent 94 pump outlet 95 eductor 96 feeding conduit 97 solidreactant storage device 98 solid metering device 99 feeder 100 inlet101, 102 pipe reactor 103 product outlet 104 vapor outlet 106 tee 110weir 111 inlet 112 post weir 113 outlet 120 inlet 121 vapor outlet 122product outlet 123 reducer 124 weir 125 next elbow 126 pipe cap 127lower end of the reducer pipe 128 tee 133 disengaging system 134 90degree elbow 135 less than 90 degree elbow 136 straight pipe 137 lessthan 90 degree elbow 138 second leg straight pipe 139 tee 140 elbow 141straight pipe line 142 flow inverter system 143 leg 144 third leg 145,146 less than 90 degree elbow 147 vapor outlet 148 product outlet 160,161, 162 flow conduit 163 injection line 164 single esterificationsection inlet 165, 166 parallel pipe reactor flow conduit 171, 172 zone173 return header 174 supply header 181 adsorber bed 182 adsorber bed183 adsorber bed 184 outlet 185 condenser 186 compressor or blower 187condensed stream 188 heat exchanger 189 inlet 190 181 bed outlet 191 182bed inlet 192 182 bed outlet 193 185 condenser outlet/183 bed inlet 194183 bed outlet 195 183 bed outlet 197 inert makeup stream 198 outlet 199inlet to condenser 211, 212, 213 esterification reactor 214 pipe reactor215 pipe reactor 216, 217 vapor outlet line 221 solids tank 222 solidsmetering device 223 weight feeder 224 recirculation line 225 pump 226heat exchanger 227 pipe reactor 228 additional pipe reactoresterification process 229 vent line 230 recycle line 231, 232 vaporline 233 heat exchanger 234 feed point 235, 236, 237 polycondensationreactors 238 gear pump 239 outlet 240 inlet line 241, 242 seal leg 243,244, 245 vent or vacuum header 246 pressure reducing device 247 seal leg251, 252, 253, 254, valve 255, 256, 257, 258, 259, 260, 261, 262 263pump 264 second pump 265 first trailer 266 second trailer 271, 272, 273,automatic valve 274, 275, 276 290 safety shower water storage tank 291safety shower outlet 292 pelletizer water distribution loop 294 filterwater storage tank 295 suitable pump 296 downstream heat exchanger 298filter 299 downstream chemical additive station 300 cutter/pelletizerstation 302 separate water line 303 downstream pump 304 cooling tower306 level control 307 water collection basin 308 cooling tower watersupply loop 310 pump 311 downstream cold water users 312 water purgeline 314 purge controller valve 315 water level control 316 polymersupply line 317 polymer extrusion die head 318 molten polymer strands320 vacuum pump 321 interstage condenser 322 first EG vapor jet 324spray condenser 325 liquid seal vessel 326 filter 328 cooler 330 secondEG jet 331 discharge line 334 vacuum line 335 condenser 336 second sealvessel 337 pump 339 downstream filter 340 chiller 343 control valve 400esterification start 401 esterification end 402 esterificationdisengagement 403 polycondensation start 404 end first stagepolycondensation 405 start second stage polycondensation 406 end secondstage polycondensation

DETAILED DESCRIPTION OF THE INVENTION

The present invention may be understood more readily by reference to thefollowing detailed description of preferred embodiments of the inventionand the Examples included therein and to the Figures and their previousand following description.

Before the present compounds, compositions, articles, devices, and/ormethods are disclosed and described, it is to be understood that thisinvention is not limited to specific synthetic methods, specificprocesses, or to particular apparatuses, as such may, of course, vary.It is also to be understood that the terminology used herein is for thepurpose of describing particular embodiments only and is not intended tobe limiting.

In this specification and in the claims, which follow, reference will bemade to a number of terms which shall be defined to have the followingmeanings:

As used in the specification and the appended claims, the singular forms“a,” “an” and “the” include plural referents unless the context clearlydictates otherwise. Thus, for example, reference to a pipe reactorincludes one or more pipe reactors.

Ranges may be expressed herein as from “about” one particular value,and/or to “about” another particular value. When such a range isexpressed, another embodiment includes from the one particular valueand/or to the other particular value. Similarly, when values areexpressed as approximations, by use of the antecedent “about,” it willbe understood that the particular value forms another embodiment. Itwill be further understood that the endpoints of each of the ranges aresignificant both in relation to the other endpoint, and independently ofthe other endpoint.

“Optional” or “optionally” means that the subsequently described eventor circumstance may or may not occur, and that the description includesinstances where said event or circumstance occurs and instances where itdoes not. For example, the phrase “optionally heated” means that thematerial may or may not be heated and that such phrase includes bothheated and unheated processes.

Residue refers to the moiety that is the resulting product of thechemical species in a particular reaction scheme or subsequentformulation or chemical product, regardless of whether the moiety isactually obtained from the chemical species. Thus, an ethylene glycolresidue in a polyester refers to one or more —OCH₂CH₂O— repeat units inthe polyester, regardless of whether ethylene glycol is used to preparethe polyester. Similarly, a sebacic acid residue in a polyester refersto one or more —CO(CH2)₈CO— moieties in the polyester, regardless ofwhether the residue is obtained by reacting sebacic acid or an esterthereof to obtain the polyester.

As used herein, a prepolymer reactor is the first polycondensationreactor, typically under vacuum, and grows the polymer chain length froma feed length of 1-5 to an outlet length of 4-30. The prepolymer reactortypically has the same function for all polyesters, but some polyestershave a target chain length that is short, such as from 10 to 30. Forthese short target chain length products, no finisher reactor (asdefined below) is required, since the prepolymer reactor will providethe end product.

A finisher reactor is the last melt phase polycondensation reactor,typically under vacuum, and grows the polymer chain to the desiredproduct chain length.

As used herein, “conventional” process or apparatus with respect topolyester processing refers to a non-pipe reactor or process, including,but not limited to, a continuous stirred tank reactor (CSTR) process orapparatus, or a reactive distillation, stripper, or rectification columnprocess or apparatus, or tank with internals, screw, or kneader processor apparatus. A typical CSTR reactor used in a conventionalpolycondensation process is a wipe or thin film reactor.

Reference will now be made in detail to the present preferredembodiment(s) of the invention, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numbers areused throughout the drawings to refer to the same or like parts.

The present invention encompasses apparatuses and methods for convertingreactants into a polyester. More specifically, in one embodiment, in afirst step, the present invention reacts starting materials (alsoreferred to as raw materials or reactants) into monomers (also referredto as polyester monomers) and then, in a second step, the presentinvention reacts the monomers into oligomers (also referred to aspolyester oligomers or prepolymers) and then into the final polyester(also referred to as polymer or polyester polymer). If materials withacid end groups are fed to the first step, such as terephthalic acid orisothalic acid, then the first step is referred to as an esterificationreaction or reactor. If the starting materials have methyl end groups,such as dimethyl terephthalate or dimethyl isothalate, then the firststep or first reactor is an ester exchange step or reactor. Forsimplicity, throughout the specification and claims, esterification andester exchange are used interchangeably and are typically referred to asesterification, but it is understood that esterification or esterexchange depends upon the starting materials. It should also beunderstood that the output from the esterification process can alsocontain oligomer in addition to the monomer. The polycondensationprocess can be one integral process or can be subdivided into twosubparts, a prepolymer process and a finishing process. In theprepolymer process, the output comprises monomer, oligomer, and polymer,with oligomer being typically in the majority. In the finishing process,typically the output from the process comprises oligomer and polymer,with the majority of the output being polymer. In the esterificationprocess, it is possible to have small quantities of polymer exit theprocess. Likewise, in the finishing process, it is possible to havesmall quantities of monomer exiting the process.

The second step is referred to as the polycondensation process orpolycondensation reactor. In this embodiment, the inlet pressurized sideof the first step or esterification reactor exits at about atmosphericpressure or above, and the output from that first step, which is fedinto the second step, is substantially monomer. In the second step, themonomer is converted to oligomer, which can, if desired, be isolated at,for example, a first pressure separation device such as a seal leg, inthe reactor. If not isolated, the oligomer is further converted to thepolymer in the pipe reactor.

In an alternative embodiment, the inlet pressurized side of the firststep exits under vacuum (in one embodiment essentially putting theprepolymer reactor on the top of the ester exchange or esterificationreactor), and oligomer is the substantial product from the first stepand is either isolated as a final product or feeds across to the secondstep in which the oligomer is reacted to form the polymer.

The invention contemplates many different arrangements for the differentreactors. In one embodiment, the esterification reactor is a separateand distinct reactor from the polycondensation reactor. Monomer isproduced in the esterification reactor and is then fed to thepolycondensation reactor to produce polymer. In another embodiment, aprepolymer reactor is put on top of the esterification reactor formingeither a separate or an integral unit, thereby producing oligomer fromthe combined esterification/prepolymer reactor, which is then fed to thepolycondensation reactor. As used herein, integral with reference to thecombination of reactors is intended to mean combining two reactorstogether such that they are in direct fluid communication with eachother and the reactors are essentially indistinguishable from each otherand from one overall reactor system. In another embodiment, thepolycondensation reactor forms an integral unit with the esterificationreactor. Reactants are inputted in the esterification reactor and thefinal polyester polymer product is produced by the integral unit. Inanother embodiment, a prepolymer reactor is used in conjuction with anesterification reactor, either as two separate units or as an integralsingular unit. The oligomer product from the prepolymer reactor isisolated as a final product. Additionally, the invention provides anesterification pipe reactor utilized to make monomer. In another aspect,the invention provides a polycondensation pipe reactor apparatus andprocess. When the esterification and prepolymer reactor are formed as anintegral unit, typically there is a vent line between the reactors tovent off the water by-product; thus, the vent line serves as thecrossover point from the esterification to the prepolymer reactor.

The process is applicable for any polyester. Such polyesters comprise atleast one dicarboxylic acid residue and at least one glycol residue; inthis context residue should be taken in a broad sense, as for example, adicarboxylic acid residue may be formed using a dicarboxylic acid or viaester exchange using a diester. More specifically suitable dicarboxylicacids include aromatic dicarboxylic acids preferably having 8 to 14carbon atoms, aliphatic dicarboxylic acids preferably having 4 to 12carbon atoms, or cycloaliphatic dicarboxylic acids preferably having 8to 12 carbon atoms. Examples of dicarboxylic acids comprise terephthalicacid, phthalic acid, isophthalic acid, naphthalene-2,6-dicarboxylicacid, cyclohexanedicarboxylic acid, cyclohexanediacetic acid,diphenyl-4,4′-dicarboxylic acid, dipheny-3,4′-dicarboxylic acid,2,2,-dimethyl-1,3-propandiol, dicarboxylic acid, succinic acid, glutaricacid, adipic acid, azelaic acid, sebacic acid, mixtures thereof, and thelike. The acid component can be fulfilled by the ester thereof, such aswith dimethyl terephthalate.

Suitable diols comprise cycloaliphatic diols preferably having 6 to 20carbon atoms or aliphatic diols preferably having 3 to 20 carbon atoms.Examples of such diols comprise ethylene glycol (EG), diethylene glycol,triethylene glycol, 1,4-cyclohexane-dimethanol, propane-1,3-diol,butane-1,4-diol, pentane-1,5-diol, hexane-1,6-diol, neopentylglycol,3-methylpentanediol-(2,4), 2-methylpentanediol-(1,4),2,2,4-trimethylpentane-diol-(1,3), 2-ethylhexanediol-(1,3),2,2-diethylpropane-diol-(1,3), hexanediol-(1,3),1,4-di-(hydroxyethoxy)-benzene, 2,2-bis-(4-hydroxycyclohexyl)-propane,2,4-dihydroxy-1,1,3,3-tetramethyl-cyclobutane, 2,2,4,4tetramethylcyclobutanediol, 2,2-bis-(3-hydroxyethoxyphenyl)-propane,2,2-bis-(4-hydroxypropoxyphenyl)-propane, isosorbide, hydroquinone,BDS-(2,2-(sulfonylbis)4,1-phenyleneoxy))bis(ethanol), mixtures thereof,and the like. Polyesters may be prepared from one or more of the abovetype diols.

Preferred comonomers comprise terephthalic acid, dimethyl terephthalate,isophthalic acid, dimethyl isophthalate,dimethyl-2,6-naphthalenedicarboxylate, 2,6-naphthalenedicarboxylic acid,ethylene glycol, diethylene glycol, 1,4-cyclohexane-dimethanol (CHDM),1,4-butanediol, polytetramethyleneglyocl, trans-DMCD, trimelliticanhydride, dimethyl cyclohexane-1,4 dicarboxylate, dimethyl decalin-2,6dicarboxylate, decal in dimethanol, decahydronaphthalane2,6-dicarboxylate, 2,6-dihydroxymethyl-decahydronaphthalene,hydroquinone, hydroxybenzoic acid, mixtures thereof, and the like.Bifunctional (A-B type where the ends are not the same) comonomers, suchas hydroxybenzoic acid may also be included.

A co-monomer, as in a conventional process, can be added anywhere alongthe process from the beginning of the esterification to thepolycondensation process. Specifically, with reference to the instantinvention, a co-monomer can be added at a location including, but notlimited to, proximate the inlet to the esterification reactor, proximatethe outlet of the esterification reactor, a point between the inlet andthe outlet of the esterification reactor, anywhere along therecirculation loop, proximate the inlet to the prepolymer reactor,proximate the outlet to the prepolymer reactor, a point between theinlet and the outlet of the prepolymer reactor, proximate the inlet tothe polycondensation reactor, and at a point between the inlet and theoutlet of the polycondensation reactor.

It should also be understood that as used herein, the term polyester isintended to include polyester derivatives, including, but not limitedto, polyetheresters, polyester amides and polyetherester amides.Therefore, for simplicity, throughout the specification and claims, theterms polyester, polyether ester, polyester amide andpolyetheresteramide may be used interchangeably and are typicallyreferred to as polyester, but it is understood that. the particularpolyester species is dependant on the starting materials, i.e.,polyester precursor reactants and/or components.

The polyesters formed by the process of the present invention arepolyester homopolymers and copolymers that are suitable for use in awide variety of applications including packaging, film, fiber, sheet,coatings, adhesives, molded articles, and the like. Food packaging is aparticularly preferred use for certain polyesters of the presentinvention. In one embodiment, the polyesters comprise a dicarboxylicacid component comprising terephthalic acid or isophthalic acid,preferably at least about 50 mole % terephthalic acid, and in someembodiments, preferably at least about 75 mole % terephthalic acid and adiol component comprising at least one diol selected from ethyleneglycol, cyclohexanedimethanol, diethylene glycol, butanediol andmixtures thereof. The polyesters may further comprise comonomer residuesin amounts up to about 50 mole percent of one or more differentdicarboxylic acids and or up to about 50 mole percent of one or morediols on a 100 mole % dicarboxylic acid and a 100 mole % diol basis. Incertain embodiments comonomer modification of the dicarboxylic acidcomponent, the glycol component or each individually of up to about 25mole % or up to about 15 mole % may be preferred. In one embodiment,dicarboxylic acid comonomers comprise aromatic dicarboxylic acids,esters of dicarboxylic acids, anhydrides of dicarboxylic esters, andmixtures thereof.

In one embodiment, the reactants comprise terephthalic acid and ethyleneglycol. In another embodiment, the reactants comprise dimethylterephthalate and ethylene glycol. In yet another embodiment, thereactants comprise terephthalic acid, ethylene glycol, and CHDM.

Preferred polyesters include, but are not limited to homopolymers andcopolymers of polyethylene terephthalate (PET), PETG (PET modified withCHDM comonomer), PBT, fully aromatic or liquid crystalline polyesters,biodegradable polyesters, such as those comprising butanediol,terephthalic acid and adipic acid residues, poly(cyclohexane-dimethyleneterephthalate) homopolymer and copolymers, homopolymer and copolymers ofCHDM and cyclohexane dicarboxylic acid or dimethylcyclohexanedicarboxylate, and mixtures thereof. In one embodiment thepolyester is PET made by reacting PTA and EG. In another embodiment, thepolyester is PETG made by reacting PTA, EG, and CHDM. In one embodiment,the reactants do not comprise an anhydride. In one embodiment, thepolyester is not polycarbonate or PBT (“polybutylene terephthalate”), orpolyesters made from phthalic anhydride or maleic anhydride.

The present pipe reactor process may also be used in esterification,polycondensation, or both, for a process wherein terephthalic acid isesterified, hydrogenated, and polymerized to form PET (or PETG if CHDMis also added), such as disclosed in U.S. Application 60/228,695, filedAug. 29, 2000, and U.S. application Ser. No. 09/812,581, filed Mar. 20,2001, which are both incorporated herein by reference.

The polyesters of the present invention may also contain small amountsof a trifunctional or tetrafunctional comonomer such as trimelliticanhydride, trimethylolpropane, pyromellitic dianhydride,pentaerythritol, or other polyester forming polyacids or polyolsgenerally known in the art. Crosslinking or branching agents may also beused. In addition, although not required, an additive(s) normally usedin polyesters may be used if desired. Such an additive includes, but isnot limited to one or more of a catalyst, colorant, toner, pigment,carbon black, glass fiber, filler, impact modifier, antioxidant,stabilizer, flame retardant, reheat aid, acetaldehyde reducing compound,oxygen scavenging compound, UV absorbing compound, barrier improvingadditive, such as platelet particles, black iron oxide, and the like.

When terephthalic acid is used as one of the reactants, typicallypurified terephthalic acid (PTA) is used as the reactant rather thanunpurified terephthalic acid (TPA) or crude TPA (CTA), although TPAand/or CTA can be used in this invention.

The processes of the present invention are directed to meltpolymerization, that is, the process of the present invention is in themelt phase, wherein the reactants are in a fluid state. This should becontrasted with solid polycondensation as used in certain polyesterprocesses of the prior art; however, the present invention includesprocesses where solid polycondensation follows liquid phasepolycondensation. The pipe reactor process of the present invention isthus appropriate for a fluid process. The polyester polycondensationprocess of the present invention should also be distinguished from otherpolymer processes, such as, for example, emulsion based polymerization,which typically requires a second or even further solvent, whereaspolyester condensation does not, and from olefin polymerization, whichis not necessarily a two-step reaction as is the case inpolycondensation. The processes of the present invention can achievecompletion or substantial completion of the esterification reaction atthe outlet of the esterification or polycondensation process. Morespecifically, the process of the present reaction, in various aspects,can achieve at least 80% completion, at least 85% completion, at least90% completion, at least 95% completion, at least 97.5% completion, atleast 99% completion, at least 99.5% completion, at least 99.9%completion, wherein completion is a term commonly used in the art tomean 100 minus the mole percent of leftover acid end groups divided bynon-acid end groups.

In addressing the present invention, the first step preferably occurs ina pipe reactor. It is also preferred that the second step, which isperformed after the first step, occur in the same or a different, secondpipe reactor. However, as one skilled in the art will appreciate, theesterification step can occur using conventional prior art processes andthen the polycondensation step can occur in a pipe reactor of thepresent invention. Similarly, the esterification step can occur using apipe reactor of the present invention and the polycondensation step canoccur using a prior art process. According to the present invention, atleast one of the first or second steps occurs in a pipe reactor.

Basic pipe reactor apparatuses as used herein are adapted as disclosedherein from those known in the art for other applications and aretypically based on standard pipes used in place of conventionalreactors. More generally, pipe reactors herein are typically an axiallyelongated, substantially cylindrically shaped apparatus, although shapesmay vary, such as square or rectangular, if not detrimental to thepurpose of the invention. In certain aspects herein, pipe reactors cansimply be hollow or empty or substantially hollow or empty pipe or tube.Hollow or empty, as defined herein, refers to the pipe or tube having noadditional devices or internal components, particularly no internalcomponents for mixing, transporting, or heating the reactor or ventfluids, such as agitators, static mixer elements, protruberences forcontrolling the fluid flow profile or mixing, packing, scrapers,rotating discs, such as, for example, those used in a wipe film or thinfilm reactor, baffles, trays, down comers, screws, or heating or coolingcoils, which are found in conventional reactors and in some pipereactors. Hollow or empty as used herein does allow for the placement offlow measuring devices, such as orifices, or flow control devices, suchas control valves or weirs, in the line. In one aspect of the invention,the pipe or tubes have a smooth interior surface. The pipe reactor ofthe present invention does not require surface area enhancementcomponents in the interior of the pipe nor does it require a filmforming enhancer as used in some of the pipe reactor designs of theprior art.

For the pipe reactors used in the first and/or second steps of thepresent invention, the criteria for choosing attributes are similar tothe criteria generally considered when building a prior art,conventional reactor. For example, the designers may consider thecriteria of the desired capacity, quality, agitation, heat transferarea, and disengagement. The designers may also consider informationdetermined from the operation and design of conventional reactors, suchas the working volume of the reactor, the heat transfer area, thesurface area of the liquid, the vapor piping velocity, the reactor vaporvelocity, the process flow rate into and out of the reactor, and theheat transfer media flow rate may also be considered. More specifically,the designers may determine the reactor volume from an existing reactor,a reactor design model, engineering calculations, or other sources ofdesign criteria. The length, l, of each pipe diameter required for eachzone of the reactor may be calculated using the reactor volume, V_(r),and the formula below:l=V _(r)/(πr ²), where r is the pipe radius.The surface area, A, required for each zone may be calculated asfollows:A=2*l*SQRT(r ²−(r−h)²),where h is the height of the liquid in the pipe and wherein r is greaterthan h.

These calculations can be reiterated for each reaction zone, taking intoconsideration heat transfer area, vapor velocity (vapor flow in moststandard reactors is vertical and in the pipe reactor will typically behorizontal), and process flow rate. In this way, the length for eachpipe diameter can be determined. It should be appreciated that not allpipe diameters will meet the requirements of all reactor conditions.FIG. 3 contains an example of the calculations. Too small a pipe sizemay create foaming problems in that foam may not break whereas too big apipe size may cause too great a pressure drop across the fluid height.The reactor is not constrained to these design criteria as other factorsmay lead to a non-optimal cost design, such as material availability orsub optimization of an area of the reactor. In certain aspects, the pipesize is from 2 inches to 24 inches, preferably 6 inches to 16 inches,more preferably 12 to 16 inches.

Reaction conditions (temperatures, pressures, flow rates, etc.) andmaterials charged to the reactor (reactants, coreactants, comonomers,additives, catalysts, etc.) can be those typically found in the priorart for the commensurate polyester reaction, but the process of thisinvention allows even wider operating conditions than used in the art.That is, the use of a pipe reactor in this present invention does notnecessarily require change in the reaction conditions or materialscharged to the reactor per se. However, reaction conditions can bedifferent and, in fact, improved with the pipe reactor system of thepresent invention. In certain embodiments, pipe reactor conditions areimproved over the prior art reactor conditions, allowing enhancedperformance, such as higher purity product (e.g., lower DEG impurity) orimproved color.

One skilled in the art can determine such parameters based on prior artmethods of making polyesters as a starting point. In one aspect, theoperating conditions in the prior art are a reactor temperature of20-400° C., preferably above the melting point of the bulk of the fluidat any given point in the reactor train, pressure from full vacuum to500 psig, a residence time up to about 8 hours, and a mole ratio of from1.005:1 to 6.00:1 on a basis of the mole ratio of the glycol residue todicarboxylic acid residue, where the acid residue can be based on theester and the glycol residue can be based on a diol. These conditions orother prior art operating conditions can be easily modified andoptimized for the pipe reactor design of this invention by one ofordinary skill in the art after consideration of the disclosures herein.

In addition to this general overview, considerations and attributes ofthe specific esterification and polycondensation pipe reactors processesand apparatuses are discussed in more detail below as well as certainother processes and apparatuses that may be used together with orseparate from the pipe reactor systems of the present invention.

The Esterification Step

With respect to the below discussion under this section ‘THEESTERIFICATION STEP,” including all subsections (Pressure Profile,Heating, etc.), unless specifically stated to the contrary, theprocesses and apparatuses of this invention discussed in this sectionbelow are equally applicable to, and can be used in, thepolycondensation processes and apparatuses.

As noted above, in one embodiment the first step involves use of a pipereactor to react the starting materials to form a monomer. In oneembodiment shown in FIG. 2, the pipe reactor 10 has an inlet 12, anoutlet 11, an exterior surface, and an interior surface. In one aspect,the interior surface of the pipe is circular, square or rectangular incross section, preferably circular, so as to form an inner diameter.

For both the esterification and polycondensation pipe reactors, the pipereactor is preferably formed of a material that is non-reactive with thematerials flowing through the interior surface, including by way ofexample steel, iron, alloys, titanium, hastalloy, stainless, carbonsteel, nickel, aluminum, copper, platinum, palladium, lithium,germanium, manganese, cobalt, zinc or a combination thereof. Othermaterials of construction include, but are not limited to, glass,ceramic, lined pipe, and plastics such asacrylonitrile-butadiene-styrene (ABS), polybutylene (PB), polyethylene(PE), poly vinyl chloride (PVC), chlorinated PVC (CPVC), polypropylene(PP), fiberglass, teflon, and a reinforced epoxy resin. Stainless steel,hastalloy and titanium are commonly used due to their properties,availabiliy and cost. For both ester exchange and polycondensation, acatalytic material may also be used for the pipe.

In use, the reactants typically are added into the pipe reactorproximal, or near, the inlet (i.e., closer to the inlet than the outlet)or adjacent to the inlet (right next to or at the inlet). As thereactants flow through the pipe reactor, the reactants react with eachother to form the monomer within the pipe reactor so that the formedmonomer exits from the outlet. However, not all of the reactants mustreact into the monomer while traversing from the inlet to the outlet(i.e., some of the reactants may exit the outlet without having reactedinto monomer) and still fall within the scope of the present invention.Additionally some of the monomer may react to form oligomer and stillfall within the scope of the present invention. The reactants added orinjected proximal or adjacent to the inlet of the pipe reactor may be inthe form of a liquid, gas, solid, or slurry, or other phase mixture.

It is easiest to add reactants as a liquid (e.g., EG and DMT) becausethe reactants may be independently pumped directly into the inlet of thepipe reactor or at another location upstream or downstream of the inlet.In one particular design, one reactant may be added via the inlet of thepipe reactor and another reactant added upstream of the inlet. In stillanother particular embodiment, one or more reactants may be addedthrough the inlet and another reactant may be added at one or aplurality of locations along the length of the pipe reactor between theinlet and outlet.

When the reactants are fluids, a pump can be used that discharges thereactants at a pressure above atmospheric pressure, typically proximalto the inlet of the pipe reactor. More specifically, a pump candischarge the reactants at a pressure sufficient for the materials totraverse through the pipe reactor and exit out of the outlet, whichinvolves overcoming frictional forces or losses, changes in potentialenergy (elevational head), and other forces that resist the flow of thematerials through the pipe reactor. The pump can be any pump known inthe art, nonlimiting examples of which include a centrifugal pump,including an in-line vertical centrifugal pump; positive displacementpump; power (piston); screw (double-end, single-end, timed, untimed);rotary (gear, multiple-rotary screw, circumferential piston, lore,rotary valve, or flexible member); jet (eductor single nozzle ormultiple nozzle); or elbow pump. The reactants can be pumped separatelyor mixed beforehand and pumped together.

Fluid reactants are easily pumped, either alone or mixed together, butsolid reactants are more problematic. As discussed in more detail below,the solid reactants can be added using a paste pump, a mix tank, aunique mix and feed system, a recirculation loop integrally formed withthe paste tank, or a combination of these apparatuses and methods.Adequate mixing is needed to dissolve any solids present in the liquid,and to provide gas/liquid mixing to drive the esterification reaction.Generally, it is preferred that the gas/liquid mixture is in a bubble orfroth state in the esterification reactor.

Pressure Profile

In the preferred embodiment, the pressure of the reactants at theinterior surface of the pipe reactor adjacent the inlet is higher, orgreater, than the pressure of the monomers and/or reactants at theinterior surface adjacent the outlet. To achieve this pressuredifferential, the inlet of the pipe reactor is preferably disposedelevationally below the outlet (as shown in FIG. 2) so that the pressuredifferential arises, in large part, from the hydrostatic pressureresulting from fluids contained within the interior surface of the pipereactor. That is, hydrostatic pressure exists between the downstream andupstream positions so that as the fluid flows upwardly through the pipereactor, the pressure decreases. The hydrostatic pressure is a functionof liquid density (temperature and composition), void fraction(reactants added, temperature, reaction by-products created, amount ofgas removed from the reactor), the height or elevational differencebetween two points in the pipe reactor, and the pressure drop due toflow in the pipe (flow rate, viscosity, pipe diameter).

The esterification pipe reactor can also take different shapes. Forexample, in one design (not shown), the pipe reactor is substantiallylinear between the inlet and outlet so that the pipe reactor is axiallyelongated. In another embodiment, the pipe reactor is substantivelynon-linear. In another embodiment, the pipe reactor has alternatinglinear and non-linear sections.

The pipe reactor can be essentially vertical, horizontal, or any anglein between. The pipe reactor orientation can form any angle with thevertical plane, from 0° (vertical, i.e. perpendicular to the ground orfoundation) to 90° (horizontal or parallel to the horizon). In variousaspects, the pipe reactor can be 0°, 10°, 20°, 45°, 60°, 75°, 85°, 89°,or 90° with respect to the vertical pane. The pipe reactor orientationangle with the vertical plane depends upon many conditions, particularlythe product being made and the pressure profile desired. For example forPET production, if terephthalic acid is used, a horizontal orientationis preferred, whereas if a DMT process is used, a vertical orientationis preferred. For PETG, a vertical orientation is preferred.

In various embodiments, the esterification pipe reactor can have avertical configuration. In various embodiments for such a verticalconfiguration, the inlet of the pipe reactor can be positioned at least20, 50, 75, 80, 90, or 100 vertical feet below the outlet. In otherembodiments the inlet can be positioned from 20 to 200, from 50 to 200,from 50 to 175, from 90 to 150, or from 100 to 140 vertical feet belowthe outlet.

Another equally viable design includes a pipe reactor that is non-linearbetween the inlet and outlet. One such design is shown in FIG. 2, inwhich the pipe reactor is serpentine in front plan view. Other profilesof the non-linear pipe reactor include, but are not limited to, designsthat are twisting; winding; twine; coil; contort; wreathe (move in acurve); convoluted; distorted; meandering; tortuous; sinuous; and/orlabyrinth.

In another design, the pipe reactor proceeds from inlet to outlet in anon-linear, horizontal run, and then proceeds vertically to a furtherlevel with another non-linear horizontal run, and this process can berepeated to any height (and width/length) desired. This creates a packeddesign with layered non-linear, horizontal runs.

In an alternative embodiment, the esterification (or polycondensation)reactor can be a series of up and down vertical rises. Specifically, theesterification reactor (or polycondensation) would be comparable to FIG.2 but rotated 90°. That is, with reference to FIG. 16, the startingmaterials are pumped in at 12 and proceed vertically upward and thenvertically downward in an alternating pattern. This design allows thefeeds to come in under pressure, then go to low pressure, and then backto high pressure, alternating subsequently back and forth. The vaporcould be removed at the low-pressure zone. The effluent exits at 11.

In these non-linear designs, the pipe reactor preferably includes aplurality of elbows disposed between the inlet and the outlet. Theelbows commonly form angles of forty-five (45) or ninety (90) degrees,but other angles are also contemplated. Each elbow changes the directionof flow within the pipe reactor as the reactants and/or monomertraverses through the elbow. The direction of the flow may changerelative to a stationary horizontal plane, such as the floor of thebuilding, or relative to a stationary vertical plane, such as a wall ofthe building, or relative to both stationary horizontal and verticalplanes. When the reactants and monomers flow through the elbows, moremixing advantageously occurs of the materials compared to a straightsection of the pipe reactor.

It is also contemplated to design the pipe reactor to obtain a desiredpressure profile. As one skilled in the art will appreciate, when thereactants and/or monomer are in a liquid form, the pressure of liquid issubstantially constant when flowing along a portion of the pipe reactorthat is horizontally oriented. That is, there is no hydrostatic pressuredifferential along a horizontal section of the pipe reactor, butfrictional losses occur as the liquids flow downstream that may vary thepressure along that horizontal section of the pipe reactor. In contrast,the pressure of the fluid decreases at an increasing rate, as thatportion of the pipe reactor is oriented more vertically flowingdownstream.

Referring now to FIGS. 10 and 11, these engineering principles may beemployed in embodiments of the present invention to create desiredpressure profiles for the reactants and/or monomer flowing through thepipe reactor. Profiles 21-25 of FIG. 11 correspond to views 21-25 ofFIG. 10. Changing the configuration of the pipe alters the pressureprofile. FIGS. 10 and 11 are correct in principle, but in actuality, thepressure drop along the horizontal pipes will only decrease by thefrictional pressure drop along the length of the pipe. The verticalconnections of the horizontal pipe segments will lead to noticeablelower pressure in the pipe reactor. Accordingly, FIG. 11 charting thepressure versus length or time would, in reality, occur in surges, notin the monatomic fashion depicted. Given this understanding of thesimplified diagrams, each configuration will be described. View 21 ofFIG. 10 is a series of pipes equally spaced, which results in a linearpressure drop in the reactor assuming equal fluid density and voidfraction. View 22 shows a pipe reactor with smaller pressure drops atthe beginning and larger pressure drops in the upper four, widelyspaced, reactor sections. The pipe reactor depicted in view 23 of FIG.10 has large initial pressure drops, caused by the increased verticalsections and smaller pressure drops in the last four sections of thereactor. View 24 shows a pipe reactor having four zones with smallpressure drop each and with a large pressure drop between each zone.View 25 design allows the reactor to drop the pressure in steps. Asalready noted, the pressure profiles for views 21 through 25 are showngraphically in FIG. 11 as profiles 21-25. It should be appreciated thatthe configurations described herein are illustrative only. Many otherconfigurations can be designed based on the principles discussed herein.

In another embodiment, it is contemplated having the inlet atapproximately the same elevational height as the outlet (i.e., the pipereactor oriented substantially horizontally) so that the pressure at theinlet will be greater than that of the outlet based on frictional lossesthat occur as the materials flow along the interior surface of the pipereactor. The pressure differential between the inlet and the outlet willnot be as great as the embodiment having the inlet elevationally higherthan the outlet. It is also within the scope of the present invention toorient the reactor pipe so that the inlet is disposed elevationallyabove the outlet.

The pressure in the top of the esterification reactor could be undervacuum with the fluid traveling upward with the vacuum. In one aspect,before the vacuum section, a vent can be used to remove the bulk of thewater. In this embodiment, the first part of the polycondensationreactor could be placed on the top of the esterification reactor. Thiswould make the plant process smaller, with part of the polycondensationprocess/apparatus on the esterification side. In another embodiment, itwould also eliminate the longest seal leg in the facility. Additionally,in another aspect, a heat exchanger can be used in the reactor lineafter the vent.

Heating

Heating the reactants increases the reaction rate to facilitate formingthe monomer and polycondensation. Accordingly, another optional featureof the present invention is to include a means for heating the reactantsand/or monomers traversing through the pipe reactor. Moreover, heatingthe materials to boil along the interior surface of the pipe reactorincreases the mixing by (1) creating a buoyancy differential between thegas/vapor formed by the boiling and the surrounding liquid (or solids)flowing along the pipe reactor and (2) breaking up the boundary layercreated by frictional forces between the interior surface of the pipereactor and the materials in contact with the interior surface. Invarious aspects, at least some of the fluids in the esterificationprocess, the polycondensation process, or both the esterification andpolycondensation processes are heated to boiling to provide efficientmixing. In other aspects, at least some of the fluids can be brought toboil by other means, such as, for example, by lowering the systempressure or adding a component having a higher vapor pressure than thefluids needing to be boiled. As one skilled in the art will appreciate,the highest heat transfer rate occurs for nucleate boiling (i.e.,generation of individual bubbles or bubble columns), but other types ofboiling are also contemplated.

The following chart provides the boiling point of exemplary componentsthat the present invention may process. Other components than thoselisted below may, of course, be used:

Component ° C. Boiling Point Temperature Acetic Acid 118.5 Adipic Acid330 Decomposing Isophthalic Acid (IPA) Sublimes Phosphoric Acid 213Terephthalic Acid 301.4 Methanol 64.5 1-Butanol 117.8 Isopropanol 82.5Titanium Isopropoxide 82.5 Titanium Dioxide greater than 475 TrimelliticAnhydride 390 Zinc Acetate 100 Loses water then sublimes Antimony Oxide1100 Cobaltous Acetate Tetrahydrate 140 Dimethyl 1.4Cyclohexanedicarboxylate 265 Dimethyl Isophthalate 282 DimethylTerephthalate (DMT) 288 Butanediol 230 Cyclohexane Dimethanol (CHDM)284-288 Diethylene Glycol (DEG) 245 Ethylene Glycol (EG) 197 TriethyleneGlycol 290

The heating means for the pipe reactor can take numerous forms. The pipereactor may be heated by a variety of media through various surfaces.More preferably, the present invention includes heat transfer media(“HTM”) that are in thermal communication with a portion of the exteriorsurface of the pipe reactor along at least a portion of the pipe reactorbetween its inlet and outlet. The heat transfer media can circumscribethe entire outer diameter of the exterior surface and extendsubstantially the full length of the pipe reactor. Heat can also beadded by inserting heat exchangers or by adding reactants hot or in thevapor state. In one aspect, in a PET or PETG process, the ethyleneglycol and/or CHDM can be added hot or in the vapor state.Alternatively, induction heating or microwave heating may be used.

A heat exchanger can be used in a reactant feed line to heat or vaporizea reactant. A heat exchanger can also be used intermediate the pipereactor, wherein the pipe reactor is in different sections and eacheffluent from one section is fed through a heat exchanger to heat thereactants and/or monomeric units. This heat exchanger intermediate thepipe reactor system is especially applicable if unjacketed pipe for thepipe reactor is utilized. Heater exchangers can be the low costcomponent of the reactor train depending upon the installed cost ofjacketed pipe vs. the installed cost of the heat exchangers. Typically,in the esterification and early polycondensation, the temperature of thefluid controls the residence time, so heat input can be the limitingdesign factor rather than the reaction kinetics. Therefore, to minimizevolume and costs, rapid heating can enhance the process. Heat exchangerscan be inserted at any location along the length of such as intermediatethe inlet and outlet or proximate or adjacent the inlet or outlet to theesterification reactor(s), the polycondensation reactor(s) or therecirculation loop or between any of the reactors (between theesterification reactors, polycondensation reactors, or between anesterification and polycondensation reactor), adjacent or proximate theinlet or outlet of any of the esterification or polycondensationreactors, or proximate, adjacent, or within any seal leg. Preferably, aheat exchanger is located at the start of each reactor section, wherethe pressure changes, since the vaporization cools the fluid. Therefore,as described below, insertion of a heat exchanger into, proximate, oradjacent the seal leg can be advantageous. If non-jacketed type pipe isused in esterification, then a low cost option is to use a heatexchanger at the beginning of the esterification process, and alsoutilize additional heat exchangers along the length of the reactor tobring the temperature back up as the by-product vaporizes. In oneaspect, the heat exchangers would be close together at the beginning ofthe esterification process and further apart later on, as the amount ofby-product vaporized is greater at the beginning of the esterification.

One example of the heat transfer media comprises a plurality ofelectrical heating components wrapped about the exterior surface of thepipe reactor. It is also contemplated using a jacket pipe circumscribingthe exterior surface, in which the jacket pipe has an inner surfacelarger than the exterior surface of the pipe reactor to form an annularspace therebetween. The heat transfer media, including by way of examplea liquid, vapor, steam, superheated water, compressed gases, condensingvapor gas, conveyed solids, electrical tracing, electrical heatingcomponents, or a combination thereof, are then located within theannular space. For use of a fluid heat transfer media (i.e., liquid,vapor, or steam), the annular space should be leak-tight in the lateraldirection so that the fluid flows longitudinally between the inlet andoutlet. More specifically, it is desired in this embodiment using fluidheat transfer media that the fluid flow within the annular space be in adirection counter to the direction of the material flowing through thepipe reactor (i.e., the heat transfer media flow from outlet to inletsince the reactants and monomer flow from inlet to outlet) althoughco-current HTM flow paths can also be used.

Based on the heat transfer media flow rate, the designers must ensurethat the velocity of the heat transfer media in the annular spacebetween the process pipe and the jacket pipe is of the appropriatevelocity for good piping design. For the present application, a speed offrom approximately four to about eighteen feet/second linear velocity isgenerally considered appropriate. If the velocity is too high, then thejacket pipe diameter must be increased.

It is also contemplated that the heat transfer media may also flow or belocated within the inner pipe and the process fluid located in theannular space between the outer surface of the inner pipe and theinterior of the exterior pipe. This design reduces the surface area ofthe process pipe and requires a larger external pipe, but may bebeneficial for some heat transfer media, such as high-pressure media.More area can be added with HTM both on the inside and the outside ofthe process fluid, with the process fluid in the middle annular space.

If more heat transfer is desired in a section of the reactor, then thesurface area to process volume ratio must be increased. This isaccomplished by using smaller diameter process pipe. The smaller processpipe will increase the process linear velocity, but as long as the flowrate is not so high that it causes pipe erosion and is not in adisengaging section of the pipe reactor, this is acceptable. Thesehigher surface area zones will affect the cost of the pipe reactor. Ifthe process flow rate is too high, then multiple parallel pipes areused.

Degassing

While flowing from the inlet to the outlet, the reactants, monomers,oligomers, polymers, and by-products may form vapor or gases as resultof chemical reactions, heating, or other reasons. The present inventionalso optionally includes a means for removing vapors from the pipereactor intermediate to its inlet and outlet and/or at, proximate oradjacent to the outlet. This removal helps to drive the reaction to afavorable equilibrium and/or to control the phase flow to the desiredregime. The removal locations can be, in certain aspects, at the end ofone or more or all zones (a “zone” referring to the esterification zoneand each polycondensation zone) and/or at one or more locations withineach reactor zone.

With reference to FIG. 20A, eight different flow regimes of two-phaseflow in horizontal pipes are shown. Dark areas represents liquid andlight areas the gas. In bubble flow, bubbles of gas move along the upperpart of the pipe at approximately the same velocity as the liquid. Inplug flow, alternate plugs of liquid and gas move along the upper partof the pipe. In stratified flow, liquid flows along the bottom of thepipe and gas flows above, over a smooth liquid/gas interface. Wavy flowis similar to stratified flow except that the gas moves at a highervelocity and the interface is disturbed by the waves traveling in thedirection of the flow. In slug flow, the roll wave is picked up by themore rapidly moving gas to form a slug, which passes through the pipe ata velocity greater than the average liquid rate. In annular flow, theliquid flows in a thin film around the inside wall of the pipe and thegas flows at a high velocity as a central core. The surface is neithersymmetrical nor smooth, but rather is similar to roll waves superimposedon squalls, as noted for wavy flow. In dispersed or spray flow, most ofthe liquid is entrained as spray by the gas. The spray appears to beproduced by the high-velocity gas ripping liquid off the crests of theroll waves. Froth flow is similar to bubble flow only with largerbubbles or void percentage. See generally, Robert S. Brodkey, “ThePhenomena of Fluid Motions,” Addison-Wesley Series in ChemicalEngineering, pp. 457-459, 1967.

For the esterification processes of this invention, froth or bubble flowin the pipe reactor is generally the optimum region to operate in, as itprovides good mixing of the vapor and liquid for facilitating thereaction. For the polycondensation step of this invention, stratifiedflow in the pipe reactor is the optimum flow regime, as it provides gooddisengagement of the vapor by-product from the liquid product.Stratified flow is also the optimum flow for the vent off of the pipereactor of this invention in either esterification or polycondensation.FIG. 20B, which is a Baker Plot on a log-log scale of By (in lb/(hrft²), a function of vapor mass velocity) versus Bx (a function of theratio of liquid to vapor mass velocities), shows the various, typicalflow regimes of two-phase flow in horizontal pipes. See generally, BakerPlots for two phase flow, e.g., in U.S. Pat. No. 6,111,064, and inPerry's Chemical Engineers' Handbook, 6th ed, pgs. 5-40 and 5-41, bothhereby incorporated by reference for the indicated purpose. As statedabove, froth or bubble is optimum for the esterification process,whereas stratified is the optimum for the prepolymer and finishing stepsof the polycondensation process. Slug and plug flow risk possibleequipment damage, annular and disbursed provide too low a residencetime, and wavy flow entrains process liquid into the gas stream, whichcauses fouling in the gas handling equipment.

In the early part of esterification, in certain embodiments, a solid canbe present, which can create a three-phase flow. However, the optimumflow regimes described above pertain to the relationship of the liquidand the gas. The solid does not, in fact, impact the gas/liquid flowregime, but it should be noted that for clarity, if a solid is present,it may not be a true two-phase flow since a third (solid) phase may bepresent.

Movement between the fluid regimes is accomplished by changing plantcapacity, increasing the recirculation rate, modifying the recirculationremoval location in the process, venting off vapor, changing the pipediameter, using parallel pipes, changing the physical parameters bymeans such as temperature, pressure, composition, adding a diluent or aninert component, or by other means.

With reference to FIG. 20B, for the esterification process, to move inthe right-hand direction on the graph, the recirculation can beincreased in an amount or ratio to achieve the froth or bubble state. Tomove upward on the graph, smaller diameter pipe is used. To move left,additional paths are used. For the polycondensation process, if thevapor velocity is too high, then additional parallel pipes can be addedto decrease the vapor velocity, in order to achieve a stratifiedtwo-phase flow regime.

FIG. 24 shows one possible set of two-phase regimes for one embodimentof the invention for a process for making PET homopolymer. In thisembodiment, the esterification reactor starts at point 400 in the frothor bubble regime and slowly moves towards point 401 as the processproceeds through the reactor. The velocity is lowered for disengagementof the two phases at point 402 in the stratified zone and then proceedsthrough the first pressure zone separator, for example, a seal leg, intothe first stage of polycondensation at point 403. The process proceedsalong the path to point 404 until the second pressure zone separator isreached moving the flow regime to point 405. The process proceeds alongthe path past point 406 to the last pressure zone separator. The lastpolycondensation zone is not shown as it is not on the scale for thisdiagram but has the same pattern as the first two zones.

Additionally, venting the gases from the system can control vapor flowand the ratio of liquid over vapor flow. Venting removes vapor. Thismoves the process down (less vapor flow) and to the right (higher ratioof liquid to gas). The embodiments below show some methods that may beused to move in any direction on the graph to change flow regimes.

Entrained gases can be vented from a pumped liquid by controlledreduction of the flow velocity of the fluid in a degassing enclosurecoupled with controlled venting of collected gas from the degassingenclosure. More preferably, it has been found that gases entrained in apumped fluid stream can be separated from the pumped liquid byincorporating a length of degas piping in the flow path of the fluidstream and releasing the separated gases through such a standpipe, or aflow-controlled vent. As used herein, the term “entrained” and liketerms, refers to undissolved gas present in a fluid; for example, gas ina fluid in the form of bubbles, microbubbles, foam, froth or the like.

In one presently preferred embodiment, the vapor removing means, ordegassing means, comprises a vent or venting mechanism incorporated intothe pipe reactor. The venting mechanism is positioned so that either allor a portion of the reactants and monomer traversing within the interiorsurface of the pipe reactor also flow through the venting mechanism whenflowing from the inlet to the outlet.

Referring now to FIGS. 7 a-7 f, the venting mechanism functions to slowthe velocity of the reactants and/or monomer in the pipe reactor to anextent sufficient to permit entrained gas to separate from the fluidreactants and/or monomer. The venting mechanism preferably produces alaminar, stratified, non-circular, two-phase gas/liquid flow. The extentof velocity reduction in the venting mechanism to provide the desiredtwo-phase (gas/liquid) flow can be determined by one of skill in the artusing (1a) the size of the gas bubbles likely present and the viscosityof the fluid, or (1b) the physical properties of both the liquid and thegas, and (2) the anticipated flow rate through the pipe reactor. Theinternal dimensions of the venting mechanism are selected to provide alarger cross-sectional area open to fluid transport than thecross-sectional area of the pipe reactor adjacent the venting mechanism.Based on mass flow rate principles, since the inner diameter increases,the velocity for a constant flow rate decreases. With the slowervelocity, the gases rise and come out of solution until the pressure ofthe released gases prevents additional gases from coming out ofsolution. Venting the released gases allows additional gases to come outof solution as the equilibrium originally existing between the gases insolution and out of solution is shifted.

For separation of entrained gases in the reactants and/or monomerdisclosed in the present disclosure, for example, it is desirable thatthe venting mechanism reduce the flow rate of the fluids flowingtherethrough and preferably a stratified two-phase flow regime isachieved in the venting and polycondensation process. The residence timeof the fluid within the venting mechanism is also controlled byappropriate selection of the length of the venting mechanism to allowsufficient time at the reduced velocity within the venting mechanism foradequate separation of entrained gas from the liquid. The appropriateresidence time for a particular fluid flow may be determined by one ofordinary skill in the art either experimentally or empirically afterconsideration of the disclosures herein.

For best results, the venting mechanism is disposed or orientedsubstantially horizontally so that the vapors and gases, within thereactants and monomer flowing therethrough flow substantiallyhorizontally and collect at the top area of the venting mechanism. Theattributes of a desirable venting mechanism allows the gases coming outof solution to be trapped by any design capable of allowing the liquidto pass on the bottom but restricting the flow of the gas on the top.

Several designs that can be used to disengage the gas from the liquidreactants and monomer include, but are not limited to, those in FIGS. 7a-7 f. Each embodiment in FIGS. 7 a-7 f has an inlet 31 to receive thefluid and gas/vapor mixture, a fluid outlet 32, a tee 36, and agas/vapor outlet 33. The venting mechanism can comprise an eccentricflat-on-bottom reducer(s) 37 to slow the velocity of the fluid into thestratified regime and to minimize the entrainment of the liquid into thevapor.

The reducer allows for a certain amount of surface area so that thevapor velocity on the liquid surface is sufficiently slow so that thevapor does not drag liquid along with it when it releases and sufficientliquid path cross-section area so that the linear velocity is slowenough that the vapor bubbles disengage from the liquid by buoyancydifferential that causes the two phases to separate. Reducers arepreferred where there is no limitation on pipe diameter or in reactorcapacity. If pipe diameters are limited and plant capacity is notlimited, an alternative to a reducer can be providing pipes and parallelto provide a lower linear velocity and more surface area in a shorterpath length.

The venting mechanism preferably has an effective inner diameter (orgreater flow area) larger than the inner diameter of the pipe reactor.Velocity can also be reduced by using multiple parallel pipes as shownin FIG. 7 f. In one aspect, the system of FIG. 7 f does not need areducer on the inlet. The configuration in FIGS. 7 e and 7 f can befurther enhanced with a weir at 38 that is in the top half of the pipe(inverted weir) between the TEEs 36 and the elbow to the right of theTEEs.

As the gases and vapors come out of solution within the ventingmechanism, they must be removed. To this end, the venting mechanismpreferably further comprises an upstanding degas stand pipe coupled tothe venting mechanism. The degas stand pipe has a receiving end in fluidcommunication with the venting mechanism and an opposed venting endpositioned elevationally above the inlet end. Although a straightembodiment is contemplated, it is preferred that the degas stand pipe benon-linear between the receiving end and the venting end.

In one embodiment, the vent further comprises an upstanding degas standpipe coupled to the vent, wherein the degas stand pipe has a receivingend in fluid communication with the vent and an opposed venting enddisposed vertically above the inlet end; and wherein the degas standpipe is non-linear extending in its lengthwise direction between thereceiving end and the venting end thereof, and wherein the degas standpipe is formed of three contiguous sections each in fluid communicationwith each other, a first section adjacent the receiving end andextending substantially vertically from the vent, a second sectioncoupled to the first section and oriented at an angle relative to thefirst section in plan view, and a third section coupled to the secondsection and oriented at an angle relative to the second section in planview so that the third section is oriented substantially horizontally.In one aspect, the vent is a first section vertical pipe coupled to athird section horizontal pipe with a second section pipe connecting thevertical and horizontal pipe at any angle other than 0 or 90 degrees,preferably at a 45 degree angle. In various aspects, substantiallyvertical, with respect to the first section, includes, the first sectionbeing oriented at an angle of from about 0 to about 60 degrees relativeto the vertical plane, from about 0 to about 50 degrees relative to thevertical plane, from about 0 to about 45 degrees relative to thevertical plane, from about 0 to about 30 degrees relative to thevertical plane, from about 0 to about 15 degrees relative to thevertical plane, or about 0 degrees (vertical) to the vertical plane; thesecond section being oriented at an angle to the vertical plane of fromabout 5 to about 85 degrees, from about 15 to about 75 degrees, fromabout 30 to about 60 degrees, or about 45 degrees; and substantiallyhorizontal, with respect to the third section, includes being orientedat an angle relative to the horizontal plane of plus or minus from about45 to about 0 degrees, plus or minus from about 30 to about 0 degrees,plus or minus from about 15 to about 0 degrees, plus or minus from about5 to about 0 degrees, or about 0 degrees. Plus or minus with respect tothe third section is intended to mean that the first and second sectionsare typically placed at an angle with respect to the vertical such thatthe vapor or gas fluid flowing therethrough proceeds in an upwardlydirection (with the liquid initially proceeding upwardly but then afterfull disengagement moving in a downwardly direction back to theprocess), whereas the third section can be oriented in an upward,horizontal, or downward orientation. In another aspect, the firstsection is oriented at from about a 0 to about a 60 degree anglerelative to the vertical plane, the second section is oriented at fromabout a 5 to about an 85 degree angle relative to the vertical plane,and the third section is oriented at from about a 0 to about a 45 degreeangle relative to the horizontal plane. In another aspect, the firstsection is oriented at 0 degrees relative to the vertical plane, thesecond section is oriented at 45 degrees relative to the vertical plane,and the third section is oriented at 0 degrees relative to thehorizontal plane. Preferably, the first section is oriented at about a45 degree angle relative to the second section, and the third section isoriented at about a 45 degree angle relative to the second section.Preferably, the third section is co-current to the process line that itis in fluid communication with, as shown in FIG. 7 g, as would be shownif the device of FIG. 7 g were to be placed or transposed directly overFIGS. 7 a-7 f where outlet 33 connects to inlet 34, or as shown in FIG.8 (assuming that the element 137 is on the same plan view plane as TEE36 or 139). However, the third section can be countercurrent, or even apoint between being co-current and countercurrent. Countercurrent canprovide for more efficient disengagement but presents equipment layoutdisadvantages. Thus, the degas standpipe creates a non-linear path fromthe first to the second section and then another non-linear path fromthe second section to the third section. In another aspect, the thirdsection is positioned at a minus 45 degree angle with respect to thehorizontal, creating a downward flow path in the third section, and forthis aspect, preferably the third section is oriented at a 90 degreeangle to the second section, which is preferably oriented at a 45 degreeangle to the vertical plane. The vent is an extremely low costconfiguration to perform a disengagement function, in that there are nomoving parts in the basic pipe design of the vent, and the vent can bemerely empty pipe.

As shown in FIG. 7 g and FIG. 8, the preferred embodiment of the degasstand pipe is formed in three contiguous sections in fluid communicationwith each other: a first section adjacent the receiving end andextending substantially vertically from the venting mechanism; a secondsection coupled to the first section and oriented at about a forty-fivedegree angle relative to the first section in plan view; and a thirdsection coupled to the second section and oriented at about a forty-fivedegree angle relative to the second section in plan view so that thethird section is oriented substantially horizontally.

A common feature is that the standpipe is vertically oriented and theventing mechanism is horizontally oriented, which creates a non-linearpath from inlet to outlet and thus allows the gas to escape without theliquid also flowing out of the standpipe. With reference to FIG. 7 g orFIG. 8, which venting mechanism arrangement is also applicable to theesterification process, the pipe lengths 136 and 145 are adjusted untila straight path from component 144 (or inlet 34 in FIG. 7 g) tocomponent 137 is not possible. Thus, no straight path exists betweeninlet 34 and exit 35. This non-linearity causes all or most of theliquid droplets in the vapor to impinge on some surface of the ventpiping. Thus, FIGS. 7 a-7 f show six different vapor disengagementarrangements, embodiments of FIGS. 7 d, 7 e, and 7 f being mostpreferred as they have no low spots that would be detrimental in adraining operation. In each embodiment of FIGS. 7 a-7 f, the embodimentof FIG. 7 g gas/vapor inlet 34 is placed in fluid communication with theoutlet 33 of venting “tee” 36 of FIGS. 7 a-7 f, such that the vaporfirst proceeds through the vertical section of FIG. 7 g, then throughthe diagonal section then through the horizontal section, and exists theoutlet 35. It is also desirable to include a flow control device withinthe degas standpipe to control the flow of fluids there through. Theflow control device may be, for example, an orifice; throttle valve;control valve; hand valve; reduced pipe section; outlet pressurecontrol; nozzle; and/or bubble through liquid for head.

The flow control device preferably allows approximately ninety percentof the vapor generated to this distance in the pipe reactor to passwhile the remaining ten percent is retained with the liquid. Thisapproximately ninety/ten percentage ratio ensures that liquid will notpass through the gas line and maintains the approximately ten percent ofthe gas for mixing in the pipe reactor. The amount of gas removed cannotapproach one hundred percent as a maximum, since the liquid would flowinto the standpipe along with the gases.

The venting end of the degas stand pipe is typically in fluidcommunication with a distillation system to which the vapors flow or areevacuated. It is also possible to vent the vapors to ambient. Thepressure at the venting end of the degas stand pipe can be controlledwhen the venting end is in communication with the distillation system,whereas when venting to ambient, the venting end will be at atmosphericpressure.

One skilled in the art will appreciate that the efficiency of vaporremoval can be improved by increasing the inner diameter of the pipereactor adjacent and prior to the venting mechanism to maximize thesurface area of the liquid and minimize the vapor velocity at thesurface half of the pipe diameter. If the velocity in the pipe in thevicinity of disengagement is too high, the pipe diameter may be expandedas shown in, for example, FIG. 7 d. In some embodiments, the expansionsections preferably have an eccentric flat-on-bottom reducer to keeppockets from forming in the reactor. These pockets reduce the reactionarea, thereby reducing capacity, and in cannot be readily drained duringthe process. The configurations shown in FIGS. 7 d and 7 f do not trapliquid and allows complete draining on plant shutdowns. The ventingmechanism can be the same size; smaller or larger in diameter than theline it is attached to. In one aspect, the venting pipe is at least onestandard pipe size larger than the pipe being vented, in another aspect,is double the size of the pipe being vented. Because the typical optimumpipe size for the pipe reactor design herein is normally the largestpipe size available, and therefore it is not practical to have a ventingpipe being larger than the pipe being vented, multiple venting pipes tolower the velocity can be used as an alternative design as shown in FIG.7 f.

If additional surface area is required or desired, additional pipes maybe installed at the same elevation, in which the additional pipes runparallel to each other and all include a venting mechanism (see, forexample, FIG. 7 f). This series of parallel pipes and venting mechanismsprovide additional area for the disengagement of gas from the reactantsand monomer.

One skilled in the art will appreciate that no gas removal is requiredto maintain the reaction within the pipe reactors, but removal of gasenhances the reaction rate by removing a limiting species. The gasremoval also reduces the void fraction making the final reactor volumesmaller.

One skilled in the art will further appreciate that multiple ventingmechanisms can be used in the pipe reactor between its inlet and outlet.For example, in one embodiment, the esterification or polycondensationreactor has at least two sections of a first section and a secondsection, and wherein the pressure is reduced in the polycondensationreactor, the reducing step comprising at least two degassing mechanismsincorporated into the polycondensation reactor so that thepolycondensation fluids traversing within its inside surface also flowsequentially by the two respective degassing mechanisms when flowingfrom the first end to the second end of the polycondensation reactor,and wherein the two degassing mechanisms are located respectively at thefirst section and the second section of the polycondensation reactor. Inone aspect, the first and second sections of the esterification orpolycondensation reactor are maintained at different pressures from eachother. In another embodiment, the esterification or polycondensationpipe reactor includes a top section, a middle section, and a bottomsection, and each of the three sections includes at least one ventingmechanism. In a particular aspect, the polycondensation reactor includesa top section, a middle section, and a bottom section, and wherein thepressure is reduced in the polycondensation reactor, the reducing stepcomprising at least three degassing mechanisms incorporated into thepolycondensation reactor so that the polycondensation fluids traversingwithin its inside surface also flow sequentially by the three respectivedegassing mechanisms when flowing from the first end to the second endof the polycondensation reactor, and wherein the three degassingmechanisms are located respectively at the top section, the middlesection, and the bottom section of the polycondensation reactor. Thetop, the middle, and the bottom sections of the polycondensation reactorcan be maintained at different pressures from each other. Another designconsideration is, as noted above, including a plurality of elbows in thepipe reactor, which can assist in removing the vapors from the reactantsand monomer. More specifically, the pipe reactor can include a firstelbow disposed upstream of the venting mechanism and a second elbowdisposed downstream of the venting mechanism.

Addition of Reactants into the Pipe Reactor

The addition of reactants was addressed above in reference to addingfluid reactants into the pipe reactor using a pump. The present sectiondiscusses alternative methods of adding the reactants into the pipereactor, including using a paste tank, a mixing tank, an alternativefeed system, and a recirculation loop.

One skilled in the art will appreciate that for each method thereactants may be added as discussed below, the reactants may be at thestandard transfer conditions or, alternatively and preferably, thereactants may be preheated before entering the reactor so that a cold,poor mixing zone does not occur. As one skilled in the art will alsoappreciate, adding cold reactants at locations upstream or downstreamfrom the inlet into the pipe reactor may be beneficial or necessary.

In some embodiments, external reactant lines for addition to the pipereactor are preferably fed from the top down into the reactor, in whichthe entry location can be any location described herein or chosen by oneskilled in the art. This reactant line should be jacketed at atemperature exceeding the melting point of the reactor contents at thelocation and the reactant feed point. Such a design keeps the reactantline from plugging when flow is stopped and (1) the control valve doesnot seal and (2) the check valve does not completely close, both ofwhich are common in prior art polyester plants.

Pumping Fluid Reactants

As discussed more thoroughly above, it is easiest to add reactants as aliquid (i.e., EG and DMT) because the reactants may be pumped directlyinto the inlet of the pipe reactor or at another location upstream ofthe inlet. The pump(s) discharge the reactants above atmosphericpressure proximal to the inlet of the pipe reactor. The reactants can beeither pumped separately or mixed beforehand and then pumped together.

Injection of Solid Materials Using a Paste Tank

The main goal of the esterification reactor is to completely react orconvert the acids in the reactor to monomers and oligomers. To maintainthis goal, solid acids, such as terephthalic acid, must be kept in thereactor until it dissolves. Paste tanks are frequently used to aid themixing and blending, and U.S. Pat. No. 3,644,483 discloses the use ofsuch a paste addition. If a paste tank is desired, the paste of anysolid can be fed into the inlet of the pipe reactor or at any locationalong the path of the pipe reactor with or without the recirculationloop, which is described below.

Mix and Feed Tank System

Referring to FIG. 15A, the mix tank 41 is filled with the liquid to beadded. Suitable liquids will dissolve or slurry with the selected solid.Suitable liquids include EG, methanol, CHDM and the like. Ethyleneglycol will be used as an example in this section. The EG is eitherheated or cooled to the appropriate temperature, depending on theadditive and the EG addition temperature, which is a function of ambientconditions and preconditioning. The heat exchanger 46, mix tank jacket,or internal coils, etc. is used to heat and cool the mix as it is beingrecirculated with pump 43 (not required when a mix tank jacket orinternal coils are used, but can be used to enhance heat and masstransfer) using temperature controller 45. The heat exchanger istypically supplied with steam 47 and water 48, but any appropriateheating and cooling media or mechanisms can be used. The additive isadded with agitator 44, pump 43 or both operating to suspend the solidsuntil they are dissolved into the EG. The level in the tank 42 ismonitored to control the addition of EG and to tell when the tank isempty for the next mix. Mix is pumped from the mix tank 41 to the feedtank 51 using pump 43 and going through a 3-way valve 60 or a pair of2-way control valves (not shown).

The feed tank 51 level 49 is controlled by adding mix from mix tank 41.When mix tank 41 is empty, the next mix is made while the residualvolume in feed tank 51 continues to feed the process. Pumps 52 and 53supply a feed header 59 to supply mix to the feed systems 57 and 58 thatcontrol the additive flow into the process. The feed tank temperature iscontrolled with temperature controller 54 using steam 55 and water 56 orany appropriate temperature control media or mechanism. Agitator 50 isused to maintain a uniform mix in the feed tank.

Pumps 52 and 53 may be installed to directly feed the polymer linewithout using a header 59. At least one pump is required per line withspares as appropriate.

An alternative system works as follows as shown in FIG. 15B. EG is addedto unjacketed pipe 72, which acts as the tank in this system. The pipe72 is located vertically in the plant, in an unused space or attached toan outside wall. The pipe 72 may have horizontal components tofacilitate installation or enhancements to the volume, but theinstallation must not have traps for the solid being dissolved. Afterthe appropriate amount of EG is added to pipe 72 as monitored by level75, the circulating pump 74 is activated. The mix system temperature iscontrolled with temperature controller 77 with steam 78 and water 76 orany appropriate temperature control media or mechanism and in this caseuses a jacketed pipe 73. The additive is added and pump 74 circulationcontinues to suspend the solids in pipe 73 until the solids aredissolved. When the solids are dissolved, valve 60 is switched to directthe flow to feed tank 82.

Feed tank 82 should have the appropriate volume to allow a mix to bemade and dumped and a second mix to be made in case the first mix is inerror. In one aspect, the inlet to tank 82 is just above the weld lineof the bottom head. The overflow of feed tank 82 is preferably at adistance of 95% of the length of the tank between the tank head weldlines. The mix from pump 74 is directed through valve 60 into feed tank82 and overflows tank 82 back into pipe 72 of the mix system via pipe71. The flow of the mix via pump 74 through both the mix system and thefeed tank provides mixing and temperature control for both systemseliminating the need for temperature control, level control, and mixing(agitation) in tank 82. Mix is added to the plant through header 59 andsystems 57 and 58. In one aspect, no pumps are required since the tank82 is strategically located at an elevation that provides head pressureto the additive systems. As mix is consumed through stations 57 and 58(two station are shown, but 1 to a large number could be used), thelevel in pipe 72 will drop. When the level in pipe 72 is so low thatpump 74 starts to cavitate, valve 60 is switched directing flow frompipe 73 back to pipe 72 without going through tank 82. During this time,the level in tank 82 will start to decline. A new mix will be made inthe mix system starting with adding EG to pipe 72 as described above.The new mix is made and diverted through valve 60 into tank 82 beforetank 82 is emptied.

The pumps 74 for the mix tanks are located on a lower floor of thebuilding. The mix tank pipe is positioned on the outside wall (or insideif space allows) to the roof, where the feed tanks 82 are located. Thepipe 73 leaving the circulating pump 74 may be jacketed for heating orcooling. The return pipe to pipe 72 may also be jacketed where necessaryor desirable. The top of the mix tank pipe 73 has a three-way valve 60leading to the feed tank 82. The feed tank 82 has an overflow line 71back to the mix tank 72. The feed tank 82 has enough residence timebetween the overflow valve and the bottom of the feed tank to feed theplant, while the next mix batch is being made. Accordingly, and whilethe next batch is being made, the three-way valve 60 is switched so thatthe fluid does not flow through the feed tank 82. This configurationeliminates all agitators and the level control in the feed tank 82. Asthe feed tanks are located on the roof, the additive flow pressure isderived from the elevation difference. Flow is controlled via a flowmeter and a control valve in stations 57 and 58. This configuration alsoreduces space required in the facility.

For a typical system consuming 100 lbs/hr through each of 2 feedstations, the pipe 72 can be 14-inch schedule 10 pipe at a length of 72feet. The pump can be 50 gallons per minute and pipe 72 can be 3 or 4inches in diameter. Tank 82 in this case would hold 75 ft³ and haveapproximate dimensions of 3.5 feet in diameter and height.

The described fluid mixing and distribution system of the invention thusincludes a first elongate and vertically disposed fluid storage vessel;a second fluid storage and dispensing vessel in fluid communication withthe first vessel, the second vessel being disposed at a greater verticalelevation than the first vessel; a circulating pump in fluidcommunication with the first vessel and the second vessel, thecirculating pump being constructed and arranged to pass a fluid flowthrough the system and to circulate the fluid from the first vessel intothe second vessel and from the first vessel to the first vessel; and acontrol valve in fluid communication with the circulating pump, thefirst vessel and the second vessel, respectively. The control valve isconstructed and arranged to selectively direct the fluid flow from thefirst vessel into the second vessel, and from the first vessel into thefirst vessel. The second vessel is in fluid communication with the plantprocess distribution system. A static pressure head formed by the fluidheld within the second vessel is used to pass the fluid from the secondvessel to the plant process distribution system.

Accordingly, an aspect of the invention is that the first vessel furthercomprises a fluid level monitor, the fluid level monitor beingconstructed and arranged to activate the control valve upon detecting apredetermined fluid level within the first vessel. In a further aspect,both of or either one of the vessels is insulated. In an additionalaspect, the first vessel is temperature controlled, the fluid flow fromthe first vessel being used to control the temperature of the secondvessel. The temperature controller further comprises a means forselectively adding steam and water to the fluid within the first vesselto raise and lower the temperature thereof, as desired. In anotheraspect, the second vessel further comprises a fluid inlet in fluidcommunication with the control valve such that the fluids are passedthrough the inlet and into the second vessel, and a fluid outlet spacedvertically above the inlet and in fluid communication with the firstvessel such that any excess fluids held in the second vessel overflowtherefrom into the first vessel. In yet another aspect, the fluid flowthrough the system is directed by the control valve from the firstvessel back into the first vessel until such time as the fluid withinthe first vessel has been mixed to a predetermined standard, and wherethe mixed fluid flow is selectively directed by the control valve fromthe first vessel into the second vessel.

An alternate embodiment of the system comprises a first fluid storagevessel; a second fluid mixing and storage vessel; a circulating pump influid communication with the first vessel and the second vessel, thecirculating pump being constructed and arranged to circulate the fluidthrough the system and from the first vessel into the second vessel; thesecond vessel being disposed at a greater vertical elevation than bothof the first vessel and the plant process distribution system; and acontrol valve in fluid communication with the circulating pump, thefirst vessel and the second vessel, respectively, the control valvebeing constructed and arranged to selectively direct the fluid flow fromthe first vessel back into the first vessel and from the first vesselinto the second vessel. The second vessel is in fluid communication withthe plant process distribution system, and a static pressure head formedby the fluid held within the second vessel is used to pass the fluidfrom the second vessel to the plant process distribution system.

The method of mixing and distribution a fluid within the fluid mixingand distribution system includes placing at least one fluid into a firstelongate and vertically disposed fluid storage vessel; passing the fluidfrom the first vessel into a second elongate and vertically disposedfluid mixing and storage vessel, the second fluid vessel being disposedat a greater vertical elevation than both of the first vessel and theplant process distribution system, with a circulating pump in fluidcommunication with the first vessel and the second vessel, thecirculating pump being constructed and arranged to pass the fluidthrough the system; using a control valve in fluid communication withthe circulating pump, the first vessel and the second vessel toselectively direct the fluid from the first vessel to either of thefirst vessel and the second vessel; and selectively passing the fluidfrom the second vessel to the plant process distribution system, thesecond vessel creating a static pressure head used to pass the fluidstored therein to the plant process distribution system.

Additional aspects of the method include adding at least one solid or asecond liquid to the at least one fluid within the first vessel andmixing the combination therein; circulating the fluid through the firstvessel until the materials therein are mixed with one another; passingthe fluid from the first vessel into the second vessel once thematerials therein have been mixed with one another; controlling thetemperature of the fluid within the first vessel; controlling thetemperature of the fluid within the first vessel by selectively addingsteam and water to raise and lower the temperature thereof, as desired;measuring the fluid level within the first vessel with a fluid levelmonitor; the fluid level monitor activating the control valve upondetecting a predetermined fluid level within the first vessel; passingany overflow fluid from the second vessel back into the first vessel.

Injection of Reactants Using Recirculation

The present invention also optionally includes a means for recirculatinga portion of the reactants and monomer flowing though the pipe reactor.As noted above, the acid paste mix tank or the mix tank can be replacedwith a recirculation or recycle loop on the ester exchange pipe reactor.

In the presently preferred embodiment, the recirculating means comprisesa recirculation loop having an influent and an effluent. The influent isin fluid communication with the pipe reactor at any point along theesterification or polycondensation process, including, but not limitedto, proximal the esterification reactor inlet, proximal the outlet ofthe esterification reactor, a point between the inlet and the outlet ofthe esterification reactor, proximal the inlet to the pre-polymerreactor, proximal the outlet to the prepolymer reactor, a point betweenthe inlet and the outlet of the pre-polymer reactor, proximal the inletor outlet to the polycondensation reactor, and at a point between theinlet and the outlet of the polycondensation reactor, and the effluentis independently in fluid communication with the pipe reactor at anypoint along the esterification or polycondensation process, includingbut not limited to, proximal the esterification reactor inlet, proximalthe outlet of the esterification reactor, a point between the inlet andthe outlet of the esterification reactor, proximal the inlet to thepre-polymer reactor, proximal the outlet to the pre-polymer reactor, apoint between the inlet and the outlet of the pre-polymer reactor,proximal the inlet or outlet to the polycondensation reactor, and at apoint between the inlet and outlet of the polycondensation reactor. Inone aspect, the effluent is in fluid communication with theesterification pipe reactor proximal or adjacent its inlet, proximal oradjacent its outlet, or at a point between the inlet and the outlet ofthe esterification reactor. In one aspect, the effluent from therecirculation is directed to the esterification reactor proximate theinlet of the esterification reactor, in another aspect, the effluent isin fluid communication with the reactor adjacent the inlet thereof, inanother aspect, the effluent is in fluid communication with the reactorbetween the inlet and outlet thereof, in another aspect, the effluentfrom the recirculation is directed to the esterification reactorupstream of the inlet of the esterification reactor, in another aspect,the influent is in fluid communication with the esterification reactorbetween the inlet and outlet thereof, in another aspect, the influent isin fluid communication with the esterification reactor proximate theoutlet thereof, in another aspect, the influent is in fluidcommunication with a second reactor, wherein the second reactor isdownstream of the esterification reactor, in another aspect, theinfluent to the recirculation is in fluid communication with thepolycondensation reactor, in another aspect, the influent to therecirculation is in fluid communication with the polycondensationreactor proximate the outlet thereof, in another aspect, therecirculating step is performed using a recirculation loop having aninfluent and an effluent, the effluent being in fluid communication withthe pipe reactor proximal the inlet, wherein the fluids flowing throughthe recirculation loop are each recirculation fluids, in another aspect,the influent being in fluid communication with the pipe reactor betweenthe inlet and outlet thereof or proximal the outlet thereof. In thisdiscussion, the reactants and monomer and any other fluid, such asoligomer and polymer flowing through the recirculation loop are referredto as the “recirculation fluids.”

As stated in another embodiment, the monomer can be provided to therecirculation loop from the polycondensation reactor, which is discussedbelow. Thus, in this embodiment, the infeed to the recirculation loop isnot from (or not solely from) the esterification pipe reactor, to whichthe effluent of the recirculation loop discharges.

In certain embodiments of the invention, which are shown in FIGS. 13 aand 13 b, the recirculation loop 91 includes a recirculation pump 92located intermediate its influent 93 and effluent 94 for increasingpressure of the recirculation fluids flowing therethrough. Therecirculation pump 92 is preferably an in-line centrifugal pump that islocated elevationally below the influent to obtain proper net positivesuction head (“NPSH”). This is because the recirculation fluids, asdiscussed in more detail below regarding the vapor removing means, areat or close to atmospheric pressure and the solution boiling point.Other pumps may alternatively be used, but a centrifugal pump is desiredbased on the pumping characteristics.

Once the recirculation fluids pass through the influent and therecirculation pump to increase the pressure, it may be desirable todecrease the pressure of the recirculation fluids, at least temporarily,at a location downstream from the recirculation pump. The advantage ofdecreasing the pressure is so that other materials, such as one or morereactants, can be drawn into the recirculation loop. The pressure ispreferably decreased using a pressure decreasing device, such as aneductor 95 through which at least a portion of the recirculation fluidsflow. The eductor pulls a slight vacuum, or sub-atmospheric pressure, atits throat. One skilled in the art will also appreciate that the eductor95 can be used interchangeably with a siphon; exhauster; venturi nozzle;jet; and/or injector or other like pressure reducing devices.

To feed or supply the reactants into the recirculation loop, a feedingconduit 96 is used that has a discharge end in fluid communication withthe recirculation line adjacent the eductor. The reactants to be fed aredrawn into the recirculation line from the decreased pressure of therecirculation fluids developed by the eductor. The feeding conduit alsoincludes a receiving end, which is opposed to the discharge end. Thevacuum on the eductor throat keeps vapor from lofting up into the solidsbeing moved into the process line. The vapor will condense on the solidsand the mixture will be very sticky and plug the system. The eductorexpansion zone has intense mixing and separates the reactant, such asPTA, so that it does not lump in the esterification piping. The solidreactant may drag gas into the reactor with it. This gas can be removedby another vapor disengagement system after the eductor. Alternately, aliquid feed to the reactor system can be fed into the solid feed hopper.The liquid will displace the gas and then the inerts will not enter theeductor.

A feeding system is used to meter and to feed selectively the solidreactants or other components, such as modifiers, catalysts, etc. intothe recirculation loop. One embodiment of a feed system is shown inFIGS. 13 a and 13 b. The first component of the feeding system is asolid reactant storage device 97, such as a silo, dust collector, or baghouse used for storing the solid reactant to be fed into therecirculation loop. Liquid can be added to the solid reactor and storagedevice to reduce or eliminate the gas entrained with the solids. If adust collector is used, then a shipping unit on scales can meter insolids by weight and the shipping container acts as the inventorydevice. Additionally, the silo can act as the weight system and shortterm inventory. If solid raw material is conveyed from offsite, then noconvey system is required. A solid metering device 98, such as a rotaryair lock, a piston and valve (hopper), double valve, bucket conveyor,blow tank, or the like, is located at the bottom of the solid reactantstorage device 97 for receiving the reactants from the solid reactantstorage device 97. The next component of the feeding system is a loss inweight feeder (or volumetric feeder) 99 that is in communication withthe solid metering device 98, and also in communication with thereceiving end of the feeding conduit 96 and intermediate 96 and 98.Thus, the reactants are fed into the recirculation loop from the solidreactant storage device 97, to the solid metering device 98, into theloss in weight feeder 99, and then through the feeding conduit 96 to bedrawn into the recirculation loop adjacent or directly into the eductor95. The loss in weight feeder 99 can also be located at the solidreactant storage device 97 or at a feed tank (not shown) locatedupstream of 97 and which feeds 97. It will also be appreciated that theaddition of solid chemical components adjacent to a pressure decreasingdevice, such as an eductor, enables addition of solid chemicalcomponents directly into any reaction fluid found within a givenchemical manufacturing process. For example, in those embodimentsutilizing an eductor as the means for decreasing the pressure of therecirculation fluids, the vacuum on the eductor throat will keep vaporsfrom lofting up into the solids that are being introduced into theprocess line. Prior to the instant invention, vapors would condense onthe solids and the mixture would become very tacky, thus resulting inthe clogging of the entire system. However, in accordance with thepresent invention, the eductor expansion or divergence zone providesvery intense mixing and maintains sufficient separation of the solidcomponent, such as terephthalic acid, so that it does not lump in thevarious reactor zones. To this end, one of ordinary skill in the artwill appreciate that for best results, it is preferred to feed the solidcomponent directly into the pressure decreasing device, such as aneductor, at any point within the divergence or expansion zone of thepressure decreasing device.

The feeding system can feed more than one solid reactant. Also, aplurality of feeding systems can operate in parallel or series. In aspecific embodiment, the polymers can be made of multiple solids andthese can be fed individually each to its own pressure reducing devicein series or in parallel, or all of the polymer solids can be meteredinto one feed hopper into one pressure reducing device. The solidpolymer could also be metered together for entering the solid reactor todevice 97. This system can thus eliminate the need for a compressor andconvey system due to gravity flow.

In one aspect, the solid reactant storage device can be on weigh cellsto perform the function of the loss in weight feeder. Also, instead ofusing weigh cells as the loss of weight feeder, a belt feed, hopperweight scale, volumetric screw, mass flow hopper, coriolis flow meter,hopper or feed bin weight loss, or the like can be used.

When the reactants added into the recirculating loop flow to theeffluent of the recirculation loop, the reactants and the otherrecirculation fluids re-enter the pipe reactor 101 adjacent or proximalthe inlet 100. Thus, this process of adding the reactants in therecirculation loop so that the reactants start near the inlet andtraverse toward the outlet perform the function of adding at least onetype of reactant into the inlet of the pipe reactor, which is one of theinitial steps in the process of the present invention. It isadvantageous to feed a solid reactant into the recirculation loop viathe feeding system so that the solid reactant is dissolved by therecirculation fluids, especially the monomer or oligomer, before flowingto the effluent of the recirculation loop.

It is also contemplated adding additional fluid reactants into therecirculation loop. The fluid reactants may be added to assist the solidreactants in dissolving in the recirculation fluids before reaching theeffluent of the recirculation loop, or as a convenience so that theadditional reactant does not need to be added separately at the inlet ofthe pipe reactor.

The fluid reactants are preferably added into the recirculation loopupstream of the eductor (before the addition point of the solidreactants), although the fluid reactants may likewise be addeddownstream of the eductor. It is contemplated adding the fluid reactantinto the recirculation loop through the recirculation pump 92 seal.Reactants can also be added upstream of the recirculation pump 92. Whenthe solid reactants are added through the feed system and the fluidreactants are also added into the recirculation loop, these processesresult in adding at least two types of reactants into the pipe reactorproximal its inlet into which the effluent of the recirculation loopfeeds.

The dissolution of the solid reactant material can be enhanced byincreasing the temperature and by changing the ratio of the polyestermonomer to solid reactant in the recirculation system, changing the feedmole ratio, and/or changing the pressure of the system.

Taking a specific example, one type of reactant fed into therecirculation loop via the feeding system can be PTA, which is a solidat room temperature. The recirculation design avoids use of a paste tankand inherent problems therewith. The fluid reactant can be, for example,ethylene glycol. Thus, if EG and PTA are the only reactants to be addedto form the monomer, then the effluent can feed directly into the inletof the pipe reactor as the only source of reactants added to the pipereactor. Of course, variations of this design are contemplated, such aspumping more of the EG reactant into the inlet of the pipe reactor, inaddition to the EG and PTA added proximal to the inlet of the pipereactor from the recirculation loop. In a separate aspect, the diol,such as EG, can be fed through the recirculation line before or afterthe recirculation loop pump or before or after the PTA feed line to therecirculation line, or upstream of but adjacent to the pressure reducingdevice along with the PTA feed.

In FIG. 13 a, one embodiment is shown where the effluent from the end ofthe esterification process is teed off 106 and one portion of theeffluent is sent to the recirculation loop. In a separate embodiment, asshown in FIG. 13 b, the tee 106 is intermediate the completeesterification process pipe reactors 101 and 102, so that the influentfor the recirculation loop is not from the end of the esterificationprocess, but rather comes from an intermediate point in theesterification process. In FIGS. 13 a and 13 b, the final effluent fromthe esterification process is at line 103 (after vapor removal in line104).

In another embodiment, the effluent of the recirculation loop is locateddownstream of the inlet of the pipe reactor. This embodiment ispreferable when the monomer that enters the influent of therecirculation loop or the slurry formed as a result of the addition atthe feeding station requires a shorter residence time than would occurif the effluent fed directly into the inlet of the pipe reactor.

In various embodiments, the influent to the recirculation loop is fromeither the esterification process or the polycondensation process.Specifically, in various aspects, the influent to the recirculation loopcan be from a point intermediate the esterification reactor (as shown inFIG. 13 b), the end of the esterification reactor (as shown in FIG. 13a), the product from the outlet of the prepolymer reactor, the productfrom the outlet of the finisher reactor, or any point from the beginningof the esterification process to the final product from the outlet ofthe polycondensation process. Thus, the recirculation fluids comprise invarious aspects the reactants, the polyester monomer, the polyesteroligomer, and/or the polyester polymer, depending upon where theinfluent from the recirculation loop originates. The recirculationsystem is not limited to the use of one recirculation loop, butalternatively comprises two or more recirculation loops configured inseries, parallel, or a combination thereof.

It is also contemplated for the recirculation loop that it includesother features discussed above for the pipe reactor, such as a heatingmeans and a vapor removing means for the recirculation loop, which maybe the same components and apparatuses discussed above and encompassingthe same features and embodiments. If monomer is removed from adjacentthe outlet of the pipe reactor a shown in FIG. 13 a, then the vaporremoving means does not have to be added to the recirculation loop.Otherwise, the liquid elevation is raised or lowered until the pressureis near atmospheric and the vapor is removed to the distillation system.

Addressing the vapor removing means specifically, in one embodiment ofthe recirculation loop, the design is similar to that described abovefor the pipe reactor as shown in, for example, FIGS. 7 a-g. Also,although not required, it is preferable that the venting mechanism belocated proximal to the influent of the recirculation loop so that thevapors are removed prior to the addition of the reactants, and such adesign is shown in FIGS. 13 a and 13 b at 104 in FIG. 13 a and 105 inFIG. 13 b.

Of note, although there are advantages with the recirculation loop thatwill be apparent to one skilled in the art based on the discussionabove, it is not necessary to include the recirculation loop for a pipereactor to fall within the scope of the present invention. Instead, thecomponents originally discussed, such as a pump for the fluid reactantsand a paste mix tank for the solid reactants can be used. Thisembodiment using the recirculation loop, however, allows the designer toreplace the paste mix tank, pump, instrumentation, agitator, etc. with apump anda pressure reducing device, such as an eductor.

One skilled in the art will also appreciate that the recirculation loopis most advantageous for injecting solid reactants and is lessadvantageous when only fluid reactants are added (e.g, forming PETmonomer from DMT and EG). Using a recirculation loop to dissolve solidreactants reduces the abrasion caused by the solids in the system. Forexample, solid PTA can be dissolved by the monomer in the recirculationloop, rather than using a conventional paste tank. In a conventionalpaste tank process, solid PTA is fed to the process and remains anabrasive component in the undissolved state. In fact, pipe reactors thatprocess only fluid reactants may not benefit from the added complexityof including the recirculation loop. However, the recirculation loop canenhance the heat transfer to the esterification process.

Weirs

A means may be included to control the level at the top of theesterification pipe reactor. In one embodiment, at least one weir isattached to the interior surface of the esterification pipe reactor andwherein the esterification fluids flow over the weir. As illustrated inFIG. 4, the desired controlling means is a weir 110. The weir ispreferably disposed proximal to the outlet of the pipe reactor.

The weir has a body portion circumscribed by an edge. A portion of theedge is referred to as the connecting edge and a remaining portion ofthe edge is the top edge. The connecting edge is of a size to becomplementarily received by a portion of the interior surface of thepipe reactor and attached thereto. Thus, since the interior surface iscircular in cross-section in the preferred embodiment, the connectingedge is also circular to complementarily contact and engage the interiorsurface.

Referring still to FIG. 4, the reactants and/or monomer is shown flowingfrom point 111 and over the weir at point 112. The weir acts as abarrier for the reactants and/or monomer so that the fluid materialflows over the top edge of the weir. Thus, the weir controls the liquiddepth along with the fluid viscosity, the flow rate, and the length ofthe pipe before the weir. After passing over the weir, the fluid flowsout of the outlet of the pipe reactor at 113. The weir, as describedbelow, may also have openings in it or at the bottom to provide flowuniformity and complete draining. This would include weirs with the topsloped, V-notched in the weirs, etc. The weir is preferably located adistance five to ten pipe diameters from the outlet of the pipe reactor.In one aspect, by sloping the top of the weir, the weir can compensatefor higher and lower flows and viscosities.

In alternative embodiments, the level can be controlled by any levelcontroller known in the art, such as, but not limited to, a controlvalve, seal legs, level devices such as those that use differentialpressure, radiation, ultrasonics, capacitance, or sight glasses. Otherspecific examples of level devices can be found in Perry's ChemicalEngineer's Handbook, 7^(th) ed., p. 8-49, which is hereby incorporatedby this reference.

Additives

Another optional aspect of the present invention comprises a means forintroducing one or more additives into the pipe reactor between itsinlet and outlet. Such additives are described above and include, butare not limited to one or more of a catalyst, colorant, toner, pigment,carbon black, glass fiber, filler, impact modifier, antioxidant,stabilizer, flame retardant, reheat aid, acetaldehyde reducing compound,oxygen scavenging compound, UV absorbing compound, barrier improvingadditive, such as platelet particles, black iron oxide, comonomers,mixtures thereof, and the like. Additives can be a solid, liquid, orgas. The additives can be preheated before entry to the system,including a phase change, such as heating EG liquid to the vapor stateto provide heat for the reactor.

In the preferred embodiments shown in FIGS. 12 a and 12 b, theintroducing means comprises a sealable channel, as represented by any ofthe arrows in FIGS. 12 a and 12 b, through the pipe reactor allowingfluid communication between its exterior surface and its interiorsurface and an injector for injecting the additive into the materialflowing within the pipe reactor (i.e., the reactants and/or monomer).The injector can include a pump or other means such as pre-pressurized,elevational, or gravity driven injection that injects the additive intothe interior of the pipe reactor, which must be performed at a pressuregreater than that of the materials within the pipe reactor at thelocation of the sealable channel.

The term “sealable channel” is meant to encompass any opening thatallows communication from outside the pipe reactor into its interior. Itis preferred that the “sealable channel” be able to be closed off sothat when the additive is not being injected into the pipe reactor, thereactants and/or monomer do not leak out of the pipe reactor. Thesealable channel may be “sealed” by a plug or the like, as well as theinjector not allowing leakage out of the pipe reactor.

The additives can be introduced or injected at any point along anyportion of the pipe reactor, as shown in FIGS. 12 a and 12 b. Examplesof suitable addition points include the sealable channel traversingthrough a portion of the top, side, or bottom of the horizontallyoriented sections of the pipe reactor, the top, side, or bottom of arespective elbow, into a seal leg, and before a heat exchanger. As shownin FIG. 12 b, injection into the elbow is advantageous because of theresulting maximum mixing and quick incorporation of the additive intothe reactants and/or monomer without high-concentration eddies occurringinside of the pipe reactor.

Another aspect of the injecting means is including a nozzle at thedischarge or outlet of the injector. The nozzle can direct flow withinthe pipe reactor at the location of the sealable channel. For example,the nozzle can inject the additive co-current, counter current, orperpendicular to the reactants and/or monomer that are flowing withinthe pipe reactor at that location.

Returning to the design of the esterification pipe reactor, the pipeelevational height, pipe diameter, total length of pipe, and pressure atthe inlet and outlet can vary widely depending upon the products made,plant capacity, and operating conditions. One of ordinary skill in theart could readily determine these parameters using basic engineeringdesign principles together with the disclosures herein.

The Polycondensation Step

With respect to the below discussion under this section, “THEPOLYCONDENSATION STEP,” unless specifically stated to the contrary, theprocesses and apparatuses of this invention discussed in this sectionbelow are equally applicable to, and can be used in, the esterificationprocesses and apparatuses.

As noted in the “Overview” section above, the second step of the processof the present invention is the polycondensation step, which in oneembodiment occurs in the polycondensation pipe reactor. Thepolycondensation step involves reacting the monomers into oligomers andthen into the polyester polymer. The monomers may be provided from thefirst step in an esterification reactor, as discussed above, or from aprior art process. Alternatively, if oligomers were substantially formedin a prepolymer first step, then oligomers are reacted directly to formthe polymer.

In a specific embodiment, when PET polymer is formed, the PET monomersare fed to the polycondensation pipe reactor. The PET monomers arereacted in the polycondensation pipe reactor to form the PET oligomerand then are further reacted preferably within the same polycondensationpipe reactor to form the PET polymer. As used herein with respect toPET, monomers have less than 3 chain lengths, oligomers have from about7 to about 50 chain lengths (components with a chain length of 4 to 6units can be considered monomer or oligomer), and polymers have greaterthan about 50 chain lengths. A dimer, for example, EG-TA-EG-TA-EG, has achain length of 2 and a trimer 3 and so on. Thus, the condensation pipereactor of the present invention can take the place of both a prepolymerreactor as well as a finisher reactor as those terms are used in theprior art and as defined hereinabove.

FIG. 4 shows the output of the pipe reactor traversing over a weir, forlevel control, and into the polycondensation reactor of the second stepof the present invention. Also referring to FIGS. 4 and 6, one skilledin the art will appreciate that pressure-restricting devices (such as,but not limited to a valve, orifice, or the like) between theesterification or ester exchange reactors and the polycondensationreactors can be used but are not required.

In one embodiment, a seal leg is used between the esterification/esterexchange reactor and the polycondensation reactor. Seal legs can also beused between some or all of the polycondensation stages. As wasdiscussed above with respect to the esterification process for thepolycondensation process, a heat exchanger can be placed proximate oradjacent to, or even within a seal leg, thereby transferring heat to thefluid between the esterification and polycondensation or between thepolycondensation stages or zones.

The static equivalent to a seal leg is a barometer. The difference inpressure between two zones of the reactor is maintained with a fluid ina ‘U’ shaped pipe. The differential in pressure will be equivalent tothe product of the fluid height times the density on the low pressureside minus the fluid height times the density on the high pressure side.One skilled in the art will recognize that if the differential height isnot great enough, the differential pressure between the zones will pushthe fluid out of the seal leg and both zones will assume an equilibriumpressure. This can require the height of the seal leg to be very largebetween zones with high pressure difference. In addition, the side ofthe seal leg on the low pressure side will generally be boiling at thereduced pressure, hence the low pressure side's density will be reducedby the void fraction of the vapor.

Fortunately, the seal leg is a dynamic barometric device in that thefluid is flowing through the seal leg. This fluid flow has associatedpressure drop with it and can be used to enhance the pressure drop ofthe low pressure side. By adding a flow path restriction, such as anorifice, valve, or small diameter piping, to the low pressure leg of theseal leg, the pressure drop on the low pressure side per unit ofelevation can be increased. If the flow restriction is inserted beforethe heat is transferred into the seal leg, then the fluid will not betwo phases and the density of will be greater. Using these methods toincrease the pressure drop of the low pressure seal leg will decreasethe total height of the seal leg.

The present invention involves providing a polycondensation reactorhaving a first end, a second end, and an inside surface defining aninner diameter. The first end can be disposed elevationally above thesecond end so that gravity moves the monomer and any formed oligomer andpolymer from the first end to the second end.

As shown in FIG. 2, the polycondensation reactor can be serpentine infront plan view (but flow is in the opposed direction as compared to theesterification pipe reactor—that is, the influent is at 11 and theeffluent is at 12 for the polycondensation process). Nonetheless, aswith the esterification pipe reactor, other profiles, such as thedesigns hereinbefore described with respect to the esterification pipereactor, are contemplated in addition to the serpentine design. It isalso preferred to include a plurality of elbows, each elbow changing thedirection of fluid flow within the polycondensation reactor. Thematerials used to form the polycondensation reactor may also be the sameas those used to form the esterification pipe reactor.

Thus, the monomer, which is preferably in a fluid form, is directed intothe first end of the polycondensation reactor so that the monomer flowsdownwardly through the polycondensation reactor. The monomer reacts toform the oligomer and then the final polymer within the polycondensationreactor so that the polymer exits from the second end thereof. As oneskilled in the art will appreciate, not all of the monomer and/oroligomer must react to be within the scope of the present invention. Themonomer, oligomer, and/or polyester polymer flowing through thepolycondensation reactor are referred to as the polycondensation fluids.

It is also preferred that the polycondensation reactor is non-linearbetween the first end and the second end to improve the masstransfer/mixing of the monomer and formed oligomer and polymer. Ingeneral and as discussed below, the polycondensation mass transfer isaccomplished by the mass transfer at the surface of the oligomer (lowmolecular weight polymer) and by the foaming action of the gas evolvingfrom within the polymer. This gas is evolved from the heating at thewall surface and the reaction within the polymer. The mass transfer isfurther enhanced as the liquid falls over optional weirs in each sectionof the reactor. The reactor can be constructed without thepolycondensation reactor weirs if the physical parameters of the polymerallows.

The polycondensation reactor can be formed as a plurality of contiguousinterconnected sections, in which the monomer, oligomer and/or polymerflows through the inside surface of each section traversing from thefirst end to the second end of the polycondensation reactor. Adjacentsections of the reactor preferably form non-linear angles with eachother.

The polycondensation reactor preferably forms an angle with avertically-oriented plane, in which the angle is greater than zerodegrees. Stated differently, each section is not parallel to thevertically-oriented reference plane and, thus, is not verticallyoriented. More specifically, the angle that each section forms with thevertically-oriented plane is between about 1 (almost verticallyoriented) and 90 degrees (horizontally oriented). The preferred angleprogresses from horizontal (90 degrees) to within about 26 degrees ofvertical; however, one skilled in the art will appreciate that thepreferred angle is based on viscosity and line rate (flow) within thepolycondensation reactor. Preferably, the sections can have differentangles relative to each other, preferably the initial sections having ahorizontal or near horizontal angle, and as the polycondensationreaction progresses and the fluid increases in viscosity, the angleincreases to provide an increased vertical sloping to facilitatetransport of the fluid through the polycondensation pipe reactor.

In one aspect, the polycondensation reaction at the top end has a lowslope (more horizontal) because the fluid is of a low viscosity, whereasthe bottom end is of a high slope (more vertical) because the fluid isof a high viscosity. The slope can be varied depending upon parameterssuch as viscosity and density of the fluid to achieve the optimumeffect. In another aspect, no slope is used in a horizontalconfiguration for the polycondensation reactor.

In one aspect, the polycondendation reactor has a general horizontalorientation rather than a vertical orientation. This horizontalorientation can include some vertical height to allow thepolycondensation fluids to flow by gravity in a downward mannerthroughout the system. In various aspect, for the horizontalconfigurations, the pipe reactor can have a length of at least 10 feet,at least 20 feet, at least 30 feet, at least 40 feet, at least 50 feet,at least 60 feet, at least 100 feet, or at least 200 feet. In otheraspects the length is from 10 to 500 feet, 20 to 250 feet, 50 to 200feet, 60 to 100 feet, or 60 to 80 feet. The upper length limit is onlylimited by the practical amount of horizontal space available at theproduction facility. In one embodiment, a pipe reactor of at least about60 feet is used because standard maximum length commercial pipe is about60 feet. Pipe reactors herein can even be hundreds of feet long or more.

In one aspect, the interior surface of the polycondensation pipe reactoris circular, square, or rectangular in cross section, preferablycircular, so as to form an inner diameter.

To aid in the mass transfer/mixing, the present invention furthercomprises a means for heating the oligomer and polymer flowing throughthe polycondensation reactor. The preferred heating means is the same asdiscussed for the esterification pipe reactor of the first step, namely,heat transfer media in thermal communication with a portion of theoutside surface of the polycondensation reactor along at least a portionof the polycondensation reactor between the first and second endsthereof or heat exchangers in series with jacketed or unjacketed pipe.In the preferred embodiment, the heat transfer media are the same asdiscussed above. In one aspect, heat exchanges can be used, preferablybetween the polycondensation zones. In a particular embodiment, heatexchangers are used in conjunction with seal legs, such as by providingthe heat exchangers proximate, adjacent, or within the seal legs used toseparate the zones.

Also similar to the esterification pipe reactor discussed above, in oneaspect, the polycondensation reactor of the present invention furthercomprises at least one weir attached to the inside surface thereof. Thepolycondensation fluids flow over the weir. The weir acts as a barrierfor the monomer/oligomer/polymer so that it flows over the top edge ofthe weir when flowing from the first end to the second end of thepolycondensation reactor. The weirs can be the same weir design and/orconfiguration described above in the esterification section. In oneaspect, a weir is used between each zone of the polycondensationreactors, and in another aspect, a weir is used between some of thezones of the polycondensation reactors but not in all zones.

The weir controls the liquid level in each pipe level of the reactor.These weirs can be as simple as a half circle or include addedcomplexities. In one aspect, by sloping the top of the weir, the weircan compensate for higher and lower flows and viscosities. In oneaspect, the design of the polycondensation pipe reactor allows theintegration of any weir design to compensate for these factors. It isalso contemplated including at least one opening though the body portionof the respective weirs so that the monomer/oligomer/polymer flowsthrough the opening, as well as over the top edge of the weir whenflowing thereby. These openings or holes in the weirs improve the flowand reduce stagnant flow zones. In still another embodiment, a sectionof the body portion of the weir may be detachably removable to allow afluid to pass through that section of the weir instead of over the weir.For example, the section may be a “V” notch or “V-slot” in the weir. The“V-slot” in the middle of each weir from the inside of the pipe to thecenter of the pipe further allows the reactor to drain when shutdown.These designs increase the mixing of the fluids when traversing by theweir.

The first pipe in each zone can be horizontal and can be functionalwithout a weir, but the weir has the advantage of increasing theefficiency of the system by both surface area and residence time.Additionally, the polycondensation pipe can be sloped downward,particularly for when the IV of the fluid approaches 0.5 dl/g orgreater.

Another aspect of the present invention that is similar to theesterification pipe reactor discussed above is that the polycondensationreactor preferably also includes a means for reducing the vapor pressurein the polycondensation reactor, such as a degassing mechanism in fluidcommunication with the inside surface of the polycondensation reactor.

Similarly, the degassing mechanism used in the polycondensation reactormay include a venting means and/or stand pipe similar to the designdiscussed above in the esterification section. Of note, the venting endof the degas stand pipe is preferably in fluid communication with avacuum source so that a sub-atmospheric pressure exists in the standpipeand at the inside surface of the polycondensation reactor. The vacuumsource may be maintained by vacuum pumps, eductors, ejectors, or similarequipment known in the art. The vacuum in each of the vapor removallines can be used to control the pressure in the zones of thepolycondensation reactor.

Referring now to FIG. 9, which shows one embodiment of theweir/degassing system, specifically, using an optional flow invertersystem for the separated liquid, the polycondensation reactor may alsoinclude a reducer 123 located immediately downstream of a weir 124inside tee 128. In one embodiment, at least one polycondensation fluidflows through a flow inverter, wherein the flow inverter is proximate toand downstream of the weir. The reducer has a diameter smaller than theinner diameter of the polycondensation reactor and the reducer forms apart of the juncture of two interconnected sections, in which theinterconnected sections are formed by an upstream section and adownstream section. The reducer is connected to the upstream section andextends into the downstream section. The reducer has a lower end 127having an aperture through which the monomer/oligomer/polymer flows whentraversing from the upstream section to the downstream section. Thelower end of the reducer 127 is spaced apart from the inside surface ofthe downstream section, which improves mixing as the fluids fall fromthe force of gravity into the inside surface of the downstream section.In fact, it is more preferred that the lower end of the reducer bespaced apart from a top or upper surface of the monomer/oligomer flowingthrough the downstream section that the fluid flowing through thereducer splatters upon the top or upper surface of themonomer/oligomer/polymer.

Stated differently and still referring to FIG. 9, in one embodiment, theinside and outside flow paths can be mixed by using a flow inverter. Bydropping over the weir 124 and into a reducer 123 before entering thenext elbow 125, the liquid monomer/oligomer/polymer will be mixed frominside out and vice versa. The liquid flows in the pipe from the left120 and passes over the weir 124, which controls the liquid depth. Thevapor continues out the right side of the tee 128 at 121. The degassedliquid flows into the concentric reducer 123. The concentric reducer 123passes through a pipe cap 126 of a larger diameter pipe. The reducedpipe stops above the liquid pool depth of the next pipe run. Theconfiguration withdraws liquid from the walls of the top pipe andintroduces the fluid into the middle of the next pipe and out at 122.FIG. 9 is but one embodiment of a flow inverter system 142; other flowinverters known in the art may also be used. Typical flow inverters usedin the art can be found in, for example, Chemical Engineers' Handbook,Perry and Chilton, Ed., 6^(th) Edition, p. 5-23. Flow inverters aretypically not needed in the esterification process, because the gastends to mix the fluid. However, a flow inverter can be used in theesterification process, if needed.

The vapor disengagement system of, for example, FIG. 8 can be usedwithout a flow inverter. In that aspect, in one embodiment, tee 139 ofFIG. 8 contains a weir such as shown in FIG. 9, but section 143 can bejust straight pipe and section 140 an elbow, without a flow invertertherein. Thus, in that aspect, section 142 of FIG. 8 and 18 do notcontain the flow inverter system of FIG. 9. Referring back to theexemplary embodiment of the polycondensation reactor shown in FIG. 2,the polycondensation reactor pipe elevations can be continuously slopedfrom top to bottom. This configuration requires extreme care incalculating the angles to obtain the desired liquid level, sincestrictly the liquid viscosity and pipe length (reaction along length)would control the angle for the level. By adding weirs to each level ofpiping, the weirs can correct errors in calculation. Even with weirs,the liquid could overflow and continue around a sloped horizontal spiralof the polycondensation piping. However, laminar flow would maintain thesame liquid on the outside and the same liquid on the inside of the flowpath.

In the polycondensation pipe reactors of the present invention, pumpsare not required between the reactor zones or sections of thepolycondensation pipe reactor. Thus, the present invention in one aspecteliminates the need for additional pumps between zones. The oligomer andpolymer in the polycondensation zones of the reactor in one aspect flowby gravity from one section to the next, and no pressure restrictingdevices are located between the reactors. Seal legs are preferably usedto maintain a pressure differential between the reactors as discussedbelow.

Referring now to FIGS. 17 a and 17 b, the polycondensation reactorpreferably includes a top section 235, a middle section 236, and abottom section 237, and at least one degassing mechanism incorporatedinto the polycondensation reactor. Such a degassing mechanism is shownin one aspect in FIG. 8 and in FIG. 18 as system 133. Only one vacuumsystem is required and only one vacuum pressure is required in thepolycondensation process. However, with only one vacuum system, thevapor velocities can be extremely high and will detrimentally put liquidwith the vapor into the vacuum system. At least two, and more preferablythree levels of vacuum can be used to minimize this entrainment. Onevacuum system can ultimately supply the one or more vacuum pressuresrequired.

If only one spray system is used, this requires that the vacuum to thehighest pressure zone be controlled with a control valve. Without aspray condenser between the reactor and the control valve, this valvewill plug. When three levels of vacuum are used, with a main spraysystem for the combined two lower pressure vacuum systems and anotherspray system for the higher pressure vacuum system, then the controlvalve is after the high vacuum spray system. This valve will not plug.One vacuum train is sufficient, but two spray systems are typicallyrequired.

With reference to FIGS. 17 a and 17 b, the effluent from theesterification reactor enters the polycondensation reactor at 235 andthe final product from the polycondensation process exits the system at239. The fluids traversing within the inside surface of thepolycondensation reactor also flow sequentially by the at least one (oneis the minimum, but additional degassing mechanisms reduces the vaporvelocity, hence reducing liquid entrainment into the vapor) respectivedegassing mechanism when flowing from the first to second end of thepolycondensation reactor, in which the as shown three degassingmechanisms are located respectively at the top section, the middlesection, and the bottom section of the polycondensation reactor. Thetop, middle, and bottom sections are preferably maintained at differentpressures from each other preferably by the use of seal legs.Preferably, for PET production, the pressure in the top section rangesfrom 40 to 120 millimeters mercury, the pressure in the middle sectionranges from 2 to 25 millimeters mercury, and the pressure in the bottomsection ranges from 0.1 to 5 millimeters mercury. One embodiment of theseal legs and vacuum source is disclosed in U.S. Pat. Nos. 5,466,765 and5,753,190, which are incorporated herein in their entirety. It is alsopreferred that the three degassing mechanisms are in fluid communicationwith one venting system. When the polycondensation pipe reactor is at asub-atmospheric pressure, the source of such vacuum can be any vacuumgenerating source such as, but not limited to, a vacuum pump or ejector.A preferred degassing mechanism 133 is shown in exploded view in FIG. 8.In one aspect, laminar mixing system 142 can be used and is shown inexploded view in FIG. 9. The elevational difference in the differentzones of the polycondensation reactor allows for the elimination of allpumps internal to the polycondensation reactor train. Thepolycondensation pipe reactor actually dampens inlet perturbationsdespite eliminating the use of pumps.

Alternatively, the various stages of polycondensation can be broken upso that the effluent (bottom) from one stage is pumped to the influent(top) of the next stage. This allows the height of the total system tobe reduced because each stage is smaller in height than the overallgravity fed system. Thus, the different vacuum sections do not need toend up with one below the next. In one aspect, the difference inpressure that is controlled in the seal leg can be used to raise thenext section of the polycondensation reactor above the exit of thehigher pressure section. A pump can be added between polycondensationvacuum pressure zones so that all zones can start at the same elevation.This lowers the total building height for the polycondensation facility.

With reference to FIG. 18, a single zone of the polycondensation reactoris shown. That is, with reference to FIGS. 17 a and 17 b, FIG. 18represents one of the zones P1, P2, or P3. Alternatively, FIG. 18 couldrepresent the entire polycondensation process. Typically, each of thezones P1, P2, and P3 is at a different pressure to maximize theefficiency in the polyester production. More or less zones can be usedfrom 1 to a plurality, for example, 2, 3, 4, 5, or more zones with 3typically be used for PET or PETG production for example. The inlet tothe zone in FIG. 18 is at 147 and the outlet at 148. Thepolycondensation fluids flow through the pipe reactor reacting from theinlet to the outlet along, in one embodiment as shown, the linear andnon-linear path. The vapor is disengaged from the polycondensationreactor with a similar piping arrangement to the esterification processat 133, as shown in FIG. 7 and as specifically shown for one embodimentof polycondensation in FIG. 8 (which were also referenced above in thediscussion of the esterification pipe reactor). FIG. 8 shows a blowup ofsection 133 of FIG. 18 where liquid and gas comes into the disengagingsystem 133. FIG. 9 shows a blow up of Section 142 of FIG. 8 and FIG. 18.FIG. 18 shows five vapor disengagement section 133. However, any numberof vapor disengagement section 133 can be used for a particular zone,from 1, 2, 3, to as many as are needed to effectively vent this system.FIG. 18 also shows an embodiment wherein the laminar mixing using a flowinverter system 142 is used, which is blown up in FIG. 9. Additionally,preferred angles for the vent system of the 90 degree angle followed bytwo 45 degree angles are shown. Other angles can also be used.

The vapor or gas in the polycondensation process should preferably bedisengaged from the liquid. For example, in one embodiment, it ispreferred to drive the EG byproduct from the polycondensation reactionoff as a vapor, disengage it, and remove it from the system. The degreeof disengagement can be affected by, for example, increasing the numberof parallel pipes, which increases disengagement

With reference to FIGS. 8 and 9, at the end of each elevation of thepolycondensation reactor 138, the liquid flows over the weir 124 insideof a tee 139 with a leg 143 directing the liquid toward the ground toelbow 140 and then horizontally at 141. The weir (or the fluid viscosityand pipe length) in the polycondensation zones maintains the liquidlevel, L, at approximately half full in the piping. This maximizes thesurface area. Once the fluid in the reactor is so thick that a weir isnot required to maintain level, then maintaining the pipe half full doesnot maximize surface area or mass transfer rates. The second leg 138 ofthe tee is in the direction of the flow. The third leg 144 of the tee ispointed in the horizontal plane in the direction away from the liquidflow. In one aspect, the vapor and entrained liquid is disengaged byflowing through a nonlinear pipe. In one aspect, the nonlinear pipe is apipe such that the angle from third leg 144 to the vapor exit does notproceed along a linear path. Such an angle creates an impingement platefor the entrained liquid. This impingement plate causes the entrainedliquid to disengage from the vapor and return back to the liquid system.With reference to FIGS. 7, 8, and 18, various embodiments of thisentrained liquid/vapor separator are shown. After a short horizontal runfrom the third tee leg, the vapor line has an elbow 134, preferably a90° elbow, directing the vapor away from the ground. The horizontal zone144 allows the vapor to flow at a slow rate and the liquid to disengageand flow back to the main stream. After a short vertical run 145 fromthe vapor elbow 134, a preferred 45° elbow 135 (common pipe componentwith a maximum disengagement vector) is installed with the vapor line atpreferably 45° elbow 146, which is again horizontal at 137. The angledpipe has a steep slope to provide the energy required for the highviscosity liquid to drain back into the reactor with very low residencetime. The vapor, without the liquid, passes upward into angled pipe.This horizontal pipe 137 is then combined with the other vapor lines oris directed to the condenser or vacuum system. The vapor leaves via line137 and the liquid goes to the next level in line 141. The steep slopeis the impingement plate for the entrained liquid. The liquid flows overthe weir, and drops to the next zone. Further polycondensation may beconducted in the next line 141. The physical layout of the pipe createsthe desired functionality (flow, pressure, etc.) without any internalparts (other than a weir) or complicated configurations.

The ester exchange or esterification vapor piping leaving tee 36 can bethe same as the polycondensation piping after the 90° elbow 134directing the vapor vertically and is shown in FIG. 7 g. As shown inFIG. 7 g, the liquid is disengaged against the angled pipe flowing backinto the liquid pool. As shown in FIG. 18, the angled pipe 136 has asteep slope to provide the energy required for the high viscosity liquidto drain back into the reactor with very low residence time. The vapor,without the liquid, passes upward into angled pipe. The gas proceeds upthe pipe and to the vapor processing equipment.

The pressure drop zone preceding the polycondensation zone has a highdegree of mixing. The pressure let down zones between reactors also hashigh mixing and are accessible in this reactor.

Nitrogen or vapor or gas can be purged across or into the liquid of oneor more polycondensation reactor sections. One potential advantage ofthis procedure is the lowering of the partial pressure of the diol,thereby increasing the polycondensation rate.

Referring now to FIG. 6 which is yet another embodiment of theinvention, the esterification reactor is shown dividing into a pluralityof parallel pipe reactor flow conduits 165 and 166, with the inlet beingat 164. The outlet of the parallel esterification reactors flow to thepolycondensation reactors. The polycondensation reactor is showndividing into a plurality of substantially parallel flow conduits 160,161, and 162 between the first and second ends thereof. Fluid flowingthrough the polycondensation reactor passes through one of the pluralityof flow conduits while flowing from the first end to the second end. Asshown, at least one of the flow conduits further comprises an injectionline 163 in fluid communication therewith, in which the injection lineadapted to add an additive to the monomer flowing therethrough. Thecontemplated additives may be any of those listed above.

Still referring to FIG. 6, the polycondensation reactor of the presentinvention can be used to manufacture multiple products from the splitline. The reactor can be split at many locations to permit theincorporation of different additives, reactants or product attributes(such as inherent viscosity (IV)). For example, in FIG. 6, one monomeror oligomer is made in a single esterification section 164 (shown withtwo parallel reactors 165 and 166), and fed to two differentpolycondensation reactors 160 and 161, allowing two different melt phaseproducts to be made. The polycondensation reactions can be the same ormay differ in conditions, reactants, additives, size, or a combinationof these features or other features. As noted above, line 163 is anaddition line and the monomer is shown as being split and an additionalreactant, such as DEG, added at 163 to allow one polycondensationreactor to make a different product, such as a higher DEG product, in162. The number of splits is not limited to two; any number of splitscan be made. Similarly, the plant could be operated with some zoneemptied and not operating, allowing the plant to operate at multiplecapacities.

Returning to the design of the polycondensation pipe reactor, the pipeelevational height, pipe diameter, total length of pipe, and pressure atthe inlet and outlet can vary widely depending upon the products made,plant capacity, and operating conditions. One of ordinary skill in theart could readily determine these parameters using basic engineeringdesign principles together with the disclosures herein. The pipeelevational height is typically not critical and can be based upon thebuilding dimensions.

HTM Subloops

Most polyester plants have numerous HTM (Heat Transfer Media, such asoil) subloop pumps. These pumps allow temperature control of individualloops that is lower than the main loop header temperature. Lowering theHTM temperature reduces the wall temperatures, improves the polymercolor, lowers degradation, and allows for better temperature control.

In the present invention, allowing the header temperature to becontrolled by the hottest zone in the reactor and valves for the otherzones can eliminate these pumps. The second hottest zone is heated bythe HTM exiting the first zone. In between the two zones, a controlvalve allows flow to the Return HTM header and then a second controlvalve allows flow from the Supply HTM header. This provides theequivalent temperature control that can be obtained with Subloop pumps.Each successive zone has temperature controlled in the same manner. Allof this is made possible because the pipe reactor can be of a jacketedpipe so the pressure drop (ΔP) of the HTM across the reactor is low. Onthe other hand, for a conventional process, a CSTR relies upon coils inthe reactor and a jacketed reactor, which causes a large ΔP of the HTMacross the reactor.

Referring to FIG. 14, the flow rate in the main HTM header can bereduced and the return temperature of the HTM will be lower than theSubloop controlled system. Heat Transfer media is supplied in header 173and returned to the furnace or heat source in header 174. A differentialpressure is applied between the headers 173 and 174 to provide drivingforce for the fluid flow. The supply header 173 pressure must alsoexceed the additive pressure drop of all of the zones piped in seriesand still overcome the pressure in the return header 174. Return header174 must provide adequate Net Positive Suction Head for the headerpumps. Heat Transfer Media (HTM) is supplied to Zone 172 through atemperature or flow control valve. The HTM leaving zone 172 proceeds tozone 171. If the fluid is too hot or the flow is too high, then HTM isremoved to header 174. If the fluid is too cold, fluid is added fromheader 173. If the fluid requires a higher temperature than can beobtained with the valve sizing, then fluid can be removed to header 174and replaced with fluid from header 173.

In a first embodiment, therefore, the heat transfer media control systemincludes a first heat transfer media header through which a first heattransfer media stream is passed; a second heat transfer media headerthrough which a second heat transfer media stream is passed; a firstheat transfer media sub-loop, through which the heat transfer media maybe passed, from the first to the second headers, respectively; and acontrol valve in fluid communication with a selected one of the headersand the first sub-loop. The pressure of the first heat transfer mediastream is greater than the pressure of the second heat transfer mediastream, and the control valve is used to selectively direct at least aportion of the first heat transfer media stream into the first sub-loopusing the pressure of the first heat transfer media stream, only, topass the heat transfer media through the first sub-loop, and to alsocontrol the temperature and pressure of the heat transfer media streambeing passed therethrough. An additional aspect of the system includes asecond heat transfer media sub-loop formed separately of the firstsub-loop and in fluid communication therewith; and a second controlvalve in fluid communication with the second sub-loop. The secondcontrol valve selectively directs at least a portion of the first heattransfer media stream into the second sub-loop, using the pressure ofthe first heat transfer media stream, to control the temperature and thepressure of the heat transfer media being passed therethrough.

In a second embodiment, the heat transfer media control system includesa first heat transfer media header through which the first heat transfermedia stream is passed; a second heat transfer media header throughwhich the second heat transfer media stream is passed; a first heattransfer media sub-loop through which the heat transfer media may bepassed from the first header to the second header; a first control valvein fluid communication with the first header and the first sub-loop; anda second control valve in fluid communication with the first sub-loopand the second header. The pressure of the first heat transfer mediastream within the first header being greater than the pressure of thesecond heat transfer media stream within the second header, and one orboth of the control valves is used to selectively direct at least aportion of the first heat transfer media stream into the first sub-loop,using the pressure of the first heat transfer media stream, to pass theheat transfer media through the first sub-loop, and to also control thetemperature and pressure of the heat transfer media stream being passedthrough the first sub-loop.

An additional aspect of the second embodiment of the invention includesadding a second heat transfer media sub-loop formed separately of thefirst sub-loop and in fluid communication therewith, with a secondcontrol valve in fluid communication with the second sub-loop whereinthe second control valve selectively directs at least a portion of thefirst heat transfer media stream into the second sub-loop, using thepressure of the first heat transfer media stream, to control thetemperature and the pressure of the heat transfer media being passedtherethrough. The second control valve is used to decrease thetemperature and the pressure of the heat transfer media passed thoughthe first sub-loop. An additional aspect of the invention includes athird control valve in fluid communication with the second sub-loop,wherein the third control valve selectively directs at least a portionof the first heat transfer media stream into the second sub-loop, usingthe pressure of the first heat transfer media stream, to control thetemperature and the pressure of the heat transfer media being passedtherethrough.

Still another aspect of the heat transfer media control system is thatthe pressure of the heat transfer media passed through the secondsub-loop will be less than the pressure of the heat transfer mediapassed through the first sub-loop. Additionally, the second controlvalve will be used to increase the temperature and the pressure of theheat transfer media passed through the second sub-loop. Thus, in anotheraspect, the system includes a conduit extending in sealed fluidcommunication from the first sub-loop to the second sub-loop so that theheat transfer media passed though the first sub-loop is passed throughthe second sub-loop, the second control valve being in fluidcommunication with each of the first and second sub-loops, respectively,and used for controlling the temperature and pressure of the heattransfer media passed from the first sub-loop into the second sub-loop.The second control valve may also be used to lower the temperature andthe pressure of the heat transfer media passed from the first sub-loopinto the second sub-loop.

Still another aspect of the system includes a series of heat transfermedia sub-loops, therefore, each subsequent sub-loop being in fluidcommunication with the immediately preceding sub-loop for receiving theheat transfer media therefrom. This features the aspect of the fluidpressure of the heat transfer media passed through the series of heattransfer media sub-loops being lower in each subsequent sub-loop withrespect to the immediately preceding sub-loop. Also, an aspect of thisembodiment of the system is that the temperature of the heat transfermedia passed through the series of heat transfer media sub-loops will belower in each subsequent sub-loop with respect to the immediatelypreceding sub-loop. An additional aspect is that each respective heattransfer media sub-loop of the series of sub-loops has a first controlvalve in fluid communication with the first header and the sub-loop forincreasing the temperature and pressure of the heat transfer mediapassed therethrough, and a second control valve in fluid communicationwith the sub-loop and the second header for decreasing the temperatureand pressure of the heat transfer media passed therethrough.

Another aspect of the heat transfer media control system is that theheat transfer media is passed from the first header into and through thefirst sub-loop in the absence of a heat transfer media circulating pump,and also that the heat transfer media is passed from the first sub-loopinto the second header in the absence of a heat transfer mediacirculating pump. Similarly, it is an additional aspect of thisembodiment that the heat transfer media is passed from the first headerinto and through the first sub-loop, and passed from the first sub-loopinto the second header, respectively, in the absence of a heat transfermedia circulating pump.

The method of passing the heat transfer media through the heat transfermedia system includes passing the first heat transfer media streamthrough a first heat transfer media header; passing the second heattransfer media stream through a second heat transfer media header;passing the heat transfer media from the first header through a firstheat transfer media sub-loop, in the absence of a heat transfer mediacirculating pump, with a first control valve in fluid communication withthe first header and the first sub-loop; and passing the heat transfermedia from the first sub-loop into the second header, in the absence ofa heat transfer media circulating pump, with a second control valve influid communication with the first sub-loop and the second header. Thepolycondensation fluids are moved from the first end of the pipe reactorto the second end thereof in the absence of a pump.

Minimization of Equipment

If desired, the use of liquid raw material feed tanks may be eliminatedfrom the polyester process. As known, raw materials are delivered to theprocess plant by any number of known types of delivery vehicles, toinclude a pipeline, a rail car, or a tractor-trailer. This inventionprovides that the raw materials, as delivered, may now be pumpeddirectly to the plant from the delivery vehicle. The basis of thisprocess is the NPSH curve of the pump. As known, and for example when atractor-trailer delivers the fluid(s) used, the NPSH is a function ofthe fluid level within the trailer and the pressure drop of the fluid tothe pump. The pressure drop is a function of the fluid velocity, thefluid viscosity, and the piping configuration used. In comparison, thehead pressure from a supply tank is a function of liquid height anddensity. The piping configuration of the system will be constant in bothinstances. The liquid density and viscosity changes should be small withambient temperature changes, but if the density and viscosity changesare large they can then be obtained from a coriolis mass flow meter, inknown fashion.

Therefore, if the mass flow rate is known from the flow meter, then aprocess control computer (not illustrated) of known construction cantake this data input, as well as any additional input data that may berequired, as discussed above, and can calculate the fluid mass withinthe trailer using the inlet pump pressure. The inlet pump pressure andflow are used to continually determine the mass of the fluid within thetrailer. During functional checkout, the pressure and flow relationshipto the fluid level within the trailer is established to correct anydeficiencies in the computer estimation.

The operating process is now described below with reference to the fluiddelivery system illustrated in FIG. 21. A first trailer 265 is parked ata pump station “P”. The trailer is connected and valved to a pump 263 byopening a series of valves 251, 252, 253, 257, 261, and 276,respectively. At the same time, a second series of valves 258, 259, 272,274, and 275, respectively, are closed. The pump 263 is started andprimed by going back to the trailer 265. The system is now ready forplant operation once the automatic valve 272 is opened. A second trailer266 is also parked at the pump station, and is connected and valved to asecond pump 264 by opening a series of valves 254, 255, 256, 260, 262and 273, respectively. Simultaneously, the valves 258, 259, 271, 274 and275 are closed. The pump 264 is started and primed by going back to thetrailer 266. The pump 264 system is now ready for plant operation but isleft in a standby mode.

The valve 272 is opened and the plant is started. When the level in thetrailer 265 is determined to be at a certain level such as, for example,10% of its full level, the valve 272 is closed and the valve 271 isopened simultaneously for providing a seamless supply of fluid to theplant. Now the pump 263 is in recirculation back to the trailer 265 andthe pump 264 is supplying the plant from the trailer 266. The plantcontinues to run consuming fluid from trailer 266 until the leveltherein is measured to be at a certain level such as, for example, 85%of the full level. Once this occurs, the computer opens the valve 275and closes the valve 276. This pumps the remainder of the fluid contentswithin the trailer 265 into the trailer 266. The pump 263 stopsautomatically on low watts. The process control computer then closes thevalve 275.

The first trailer 265 is removed from the pump station, and anothertrailer 265 full of the desired process fluid is parked at the pumpstation. This process is repeated with pump 263 being primed from thetrailer 265. Then, once the fluid level within the trailer 266 ismeasured to be at a certain level such as, for example, 10% of fullvalue, the valve 271 is closed and the valve 272 is opened. The fluidlevel in the trailer 265 is used until the fluid level is measured at acertain level such as, for example, 85% of full, whereupon the remainderof the fluid within the trailer 266 is pumped into the trailer 265. Thetrailer 266 is then removed from the pump station, and another fulltrailer 266 is parked in the position of the original trailer. The pump264 is fed and primed from the new trailer 266, and the processcontinued in this fashion.

A first embodiment of the described fluid delivery system thereforeincludes at least one delivery container positioned at a pump station,and at least one pump in fluid communication with the at least onedelivery container, the at least one delivery container being in fluidcommunication with a valve train, the valve train being in fluidcommunication with the process plant pipe system. The fluid isselectively pumped directly from the at least one delivery containerthrough the valve train and into the process plant pipe system in theabsence of a fluid delivery feed and storage tank for otherwisereceiving and storing the fluid from the at least one delivery containertherein. Additionally, the system includes a second delivery containerpositioned at the pump station and a second pump in fluid communicationwith the second delivery container, each of the delivery containers andpumps, respectively, being in fluid communication with the valve train.The valve train is comprised of a plurality of selectively operablecontrol valves and being in fluid communication with the process plantpipe system, such that the fluid is selectively pumped directly from thefirst and second delivery containers, respectively, through the valvetrain and into the process plant pipe system in the absence of a fluiddelivery feed and storage tank.

Additional aspects of the system include a process control computer, theprocess control computer being operably coupled to the first and thesecond pumps, respectively, and to at least one of the control valveswithin the valve train; a mass flow meter in fluid communication witheach of the first and the second delivery containers, respectively, andbeing operably coupled to the process control computer; the mass flowmeter being constructed and arranged to measure and transmit a fluidmass flow rate of the fluid pumped from either of the deliverycontainers to the process control computer; the process control computercalculating the fluid mass within a selected one of the deliverycontainers using the fluid mass flow rate and a measured inlet pumppressure. Additionally, the process control computer uses the inlet pumppressure and fluid flow rate flow to continually determine the mass ofthe fluid within the selected one of the delivery containers.

The process control computer opens a first automatic control valve andstarts the operation of the process plant; and closes the firstautomatic control valve once the fluid level within the first deliverycontainer is determined by the process control computer to be at a firstpredetermined fluid level. An additional aspect is that a secondautomatic control valve is simultaneously opened by the process controlcomputer such that the first pump recirculates the fluid from the firstdelivery container back into the first delivery container, and thesecond pump supplies the fluid from the second delivery container to theprocess plant. The plant is thereafter provided with the process fluidfrom the second delivery container until the fluid level therein isdetermined by the process control computer to be at a secondpredetermined fluid level. Thereafter, the process control computeropens the first control valve and closes the second control valve suchthat the remainder of the fluid contents within the first deliverycontainer are pumped into the second delivery container. Once theprocess control computer closes the first control valve, the firstdelivery container may be replaced with a fresh delivery container inits place at the pump station. An additional aspect of the inventionincludes the process control computer reopening the second control valveand closing the first control valve such that the plant is provided withthe process fluid from the second delivery container.

The described method of this invention therefore includes positioning afirst delivery container at a pump station, the first delivery containerbeing in fluid communication with a first pump, positioning a seconddelivery container at the pump station, the second delivery containerbeing in fluid communication with a second pump, and selectively pumpingthe fluid from each of the respective delivery containers directly intothe valve train and into the process plant pipe system. This methodincludes the aspects of operably coupling the process control computerto the first and the second pumps, respectively, and to at least one ofthe control valves within the valve train, and using a mass flow meterin fluid communication with each of the first and the second deliverycontainers, respectively, and being operably coupled to the processcontrol computer, to measure the fluid flow passed therefrom by thefirst and second pumps, respectively. The process control computercalculates the fluid mass within a selected one of the deliverycontainers using the fluid mass flow rate and a measured inlet pumppressure, and also uses the inlet pump pressure and the fluid flow rateflow and continually determining the mass of the fluid within theselected one of the delivery containers. The process control computeropens a first automatic control valve and starts the operation of theprocess plant in response to determining the mass of the fluid withinthe selected one of the delivery containers.

Additional aspects of the method also include the process controlcomputer closing the first automatic control valve once the fluid levelwithin the first delivery container is determined by the process controlcomputer to be at a first predetermined fluid level such that the firstpump recirculates the fluid back into the first delivery container, andsimultaneously opening a second automatic control valve such that thesecond pump supplies the fluid from the second delivery container to theprocess plant; providing the process plant with the process fluid fromthe second delivery container until the fluid level therein isdetermined by the process control computer to be at a secondpredetermined fluid level; the process control computer opening thefirst control valve and closing the second control valve such that theremainder of the fluid contents within the first delivery container arepumped into the second delivery container; the process control computerclosing the first control valve and replacing the first deliverycontainer with a fresh delivery container at the pump station; and thentransferring the remainder of the fluid from within the first deliverycontainer to the second delivery container, and thereafter continuing toprovide the process plant with the process fluid from the seconddelivery container while replacing the first fluid delivery container.

As known, in a typical polyester processing facility three differentdistillation columns are present: A water column, a stripper column, andan MGM column (mixed glycol and monomer column or ethylene glycolcondensate column). Vapor from the esterification reactor is sent to thewater column. There water is separated from the ethylene glycol. Lowboilers (including water) are removed at the top of the column and sentto the stripper column, while ethylene glycol and other high boilers areremoved at the bottom of the column and can be sent back to the pastetank, the reactors, directed to other users, and as described herein,back to the recycle loop.

The stripper column separates paradioxane out at the top of the strippercolumn which cannot be sent to the waster water treatment facility, andcombines the paradioxane with an azeotrope of water which is then sentto the furnace or to an oxidizer with the other low boiling pointcomponents. The fluids from the bottom of the stripper column are sentto the wastewater treatment facility. In one embodiment of the presentinvention, the water column is maintained by sending the low boilers tothe furnace rather than to the stripper column, and the stripper columncan be eliminated. In this instance, the water column is vented to thefurnace rather than sending the low boilers to the stripper column. TheMGM column is also vented to the furnace.

It is also known that in a conventional polyester processing facility, awastewater treatment facility is required to treat the organic waste aswell as the hydraulic load (water flow) resulting from the process. Inone aspect of the present invention, described above, the organic wasteis vented to the furnace where it is burned. In a separate aspect of theinvention, and as discussed in detail herein, by eliminating many unitoperations from the polyester formation process and integrating theplant, thus creating a more compact plant, a roof can be put over theentire process plant, thus eliminating the need to send the hydraulicload to a wastewater treatment facility because rain water will nolonger be permitted to come into contact with the process equipment,and/or any spilled process fluids. In still another aspect of theinvention, therefore, the elimination of the organic wastes by sendingthese to the furnace, and the elimination of hydraulic load orwastewater by integrating the plant through the reduction of thefacility size coupled with putting a roof over the facility, eliminatesthe need for a wastewater treatment facility needed to otherwise servicethe polyester processing plant.

Environmental emissions from the plant can be reduced by venting all ofthe process (i.e., the distillation columns, the scrubbers, theadsorbers, the vacuum pumps, etc,) and tank vents into a pressurizedvent header. The vent header flows to the HTM furnace and isincinerated. If all such vents are connected to this header, therefore,the unoxidized emissions from the plant will be reduced by more than 99%(typically oxidized emissions are carbon dioxide and water).Additionally, this process eliminates the need for a stripper column.Still another feature of the present invention is that by increasing thevolume of the base portion of the respective distillation columns overthat base volume used in conventional processes, tanks for the productspassed to and from the distillation columns can be eliminated. Thisreduces the amount of fluid containment area and all of the associatedcosts with any such storage tanks. Increasing the height or diameter ofthe base can increase the distillation column volume. No additionalinstruments are needed on the column. In one aspect of the invention,the base of the water column is at least 40% larger in diameter orheight than a conventional water column. In this aspect, the overallheight increases by about at least 3%. In another aspect, the base isincreased at least 50% in diameter or height.

The wastewater treatment facility can be eliminated, as discussed above,through the integration of the plant. This is particularly made possibleby eliminating environmental emissions and by eliminating storage tanksas previously discussed. Moreover, the plant is constructed with a roofover all process buildings, the trailer pump/unloading station, the HTMfurnace, and/or any other areas of the plant that could have thepotential of COD. The wastewater from the pelletizer and the coolingtower are separated from all other waste streams and go to the plantoutfall. All rainwater, including water from all roof areas describedabove, also goes to the plant outfall. A ditch, preferably doublewalled, is constructed between the process plant and the HTM furnace.This preferably is a covered ditch. All remaining contaminatedwastewater goes into the ditch. All collected wastewater within theditch is pumped from the ditch to the HTM furnace where the wastewateris burned. The heat duty cost is offset by the reduction in the cost forthe capital and operating cost of a wastewater treatment plant if allother sources of water are limited.

Also, if the plant layout is planned properly, only one convey system isrequired for the pellets or chips for a melt phase facility. The finalreactor outlet is high enough so that the cutter can make pellets, whichwill fall by gravity into the analysis bins located below the cutters.In another embodiment, the analysis bins are eliminated. The pellets areconveyed to the top of the blending silo, and the bottom of the blendingsilo is positioned above the packaging bin. The bottom location andelevation of the packaging bin are high enough to allow the contents ofthe packaging bin to feed by gravity into Sea bulks, trucks, or railroadcars. The packaging bin can also be eliminated by directly feeding thepackaging equipment from the silo. The units that package bulk bags,boxes, drums, and sacks are located under and near enough to thepackaging bin so that they can also be filled by gravity. The reductionin convey systems reduces equipment, utility cost, and improves productquality with the elimination of the mechanism for the melting and thestringing of the pellets.

In still another aspect of the invention, the water systems in the plantcan be minimized by combining the safety shower, the cooling tower, thecutter water, and the HTM pump coolers.

Typically, the plant safety shower system is a self contained system. Ithas a level control system fed off of the city water supply. It also hasa pressurization system and a back up pressurization gas in case of apower failure. The cooling tower has a water supply used to maintain thewater level therein due to the loss of water that evaporates, and ablowdown (purge) to keep high boiling point components fromconcentrating or precipitating. The cooling tower system has a chemicaladditive system that keeps the water pH, hardness, biological growth,and the like on target. The cutter water system supplies water to thecutter (making pellets), and make-up water is required since the waterevaporates when contacting the hot polymer strands. This system does notnormally have a purge, and the impurities generally leave on thepellets, although this can cause problems. The cutter system also has achemical additive system. The HTM pumps have coolers that have ahigh-pressure drop. The standard cooling tower header does not supplyenough pressure to go through the high-pressure drop coolers on the HTMpumps.

Four choices typically exist for dealing with these problems:

1) use supply water as once through cooling;

2) increase the pressure of the cooling tower water header paying theincreased capital and pumping costs;

3) build a separate high pressure cooling tower header incurring theincreased capital and pumping cost; and

4) purchasing low pressure drop coolers for the pumps incurring theadded capital cost and voiding the warrantee.

Integrating these systems could reduce capital and operating costs. Withthe integration of the HTM systems and the elimination of all Sublooppumps, only the main loop HTM pumps are left. The cooling water flowrequired for these HTM pumps is slightly less than the cooling towermakeup water required (too much water is acceptable). The cutter watersystem has higher water pressure to go to the cutters, the pressure ofwhich is also high enough for use with the HTM pump coolers. However,after passing through the HTM pumps the water should not come back tothe cutter system since an HTM leak would contaminate the product.Therefore, this water from the HTM pumps should go to the cooling tower.If the cooling tower chemicals were added to the cutter water system, itwould protect the cutter water system and eliminate one of the chemicaladditive systems and still supply the chemicals to the cooling tower viathis purge. A purge on the cutter water system would not be detrimentaland could be beneficial. Pumping water from the cutter water systemthrough the HTM pump coolers and then through the cooling tower wouldeliminate the additional cooling system needed for the HTM pumps, wouldeliminate a chemical treatment system, and provide the needed water toall three uses. Water would still need to be supplied to the cutterwater system and the safety shower.

The safety shower system needs to be purged weekly to keep the waterfrom being stagnant. Purging more often that this would be beneficial,and an automatic purging would reduce cost. If the safety shower tank iselevated then the pressurization and back up pressurization systemtherefor are not needed. If water entered the safety shower tank andoverflowed out the top of the tank, then the tank would stay full andnot need a level system. If the level control valve for the cutter watersystem was in the line supplying the safety shower tank, and the safetyshower tank overflowed into the cutter water tank, then the safetyshower would be continuously purged with water flowing at the make-uprate for both of the cutter water and the cooling tower water systems.This layout would eliminate all labor and instruments from the safetyshower system.

A novel integrated plant water distribution system of the inventionwhich addresses the aforementioned problems, and satisfies the needs ofthe plant operator, is illustrated in FIG. 22. Referring now to FIG. 22,a safety shower water storage tank 290 is supplied with clean freshwater from a suitable water source “W”, such as an off-site city watersupply (not illustrated). The safety shower tank supplies any neededwater to the plant safety showers and eyebaths (not illustrated), andalso supplies water through a first pipeline 291 to a filter and waterstorage tank assembly 294 provided as a part of a separatecutter/pelletizer water tank 294. Once introduced into the waterdistribution loop, the water is passed into and through the filter andwater storage tank assembly 294. From here the filtered and cold wateris passed through the pelletizer water distribution loop by a suitablepump 295, and then passed through a downstream heat exchanger 296 tocool the water after having been passed through the pump. A filter 298is positioned in the pelletizer water distribution loop downstream ofthe pump to remove any dirt and/or small particles that may be entrainedtherein. A downstream chemical additive station 299 is provided as apart of the pelletizer water distribution loop in order to keep thewater in the pelletizer water distribution loop within controlledorganic growth, water hardness, water solubility, and corrosivityguidelines, as needed for the process being performed, as well as beingdue to the locale and water characteristics of the water supplied to thesystem. The last component of the pelletizer water distribution loop isa cutter/pelletizer station 300, the function of which is describedbelow.

Molten polymer from the plant is supplied via polymer supply line 316 toa polymer extrusion die head 317 at the cutter/pelletizer station 300,the die head extruding a plurality of molten polymer strands 318 inknown fashion. The molten polymer strands are cooled in thecutter/pelletizer station 300 for pelletizing and/or cutting the moltenpolymer strands with the cold, filtered water supplied through thepelletizer water distribution loop. Thereafter, the now heated and“dirty” water is passed into the filter and water storage tank assemblyto be cooled, with make up water for water lost from evaporation at thecutter/pelletizer station, which make up water is also used to purge topump 303, added from the safety shower water storage tank. The waterpassed into the filter and water storage tank assembly is then passedback through the pelletizer water distribution loop, as describedhereinabove, for re-use.

A separate water line 302 is fed from the pelletizer water distributionloop, and extends to a downstream pump 303 used to pass the water to acooling tower 304. The cooling tower is provided with a level control306, used to maintain the level of water held in a water collectionbasin 307 formed as a part of the cooling tower assembly. The levelcontrol 306 has a minimum flow setting that will ensure that asatisfactory amount of water is always provided for the minimum requiredcooling flow for the pump 303. The cooling tower cools the water passedtherethrough, the water being passed from the water collection basinthrough a cooling tower water supply loop 308.

The anticipated uses of the water passed through the cooling tower watersupply loop include any desired number of downstream cold water users311, which users may return the now “waste” water to the cooling towerwater supply loop. Any water not used downstream is passed back into andthrough the water cooling tower, the level control valve 306 drawingwater from the pelletizer water distribution loop as needed to make upfor lost water within the collection basin/reservoir 307.

The waste water passed back into the cooling tower water supply loopfrom the downstream users is passed back into and through the coolingtower 304, and evaporates therein. The evaporation of the water thusconcentrates solids and/or contaminates within the water stream passedthrough the cooling tower water supply loop, so water is purged out ofthe loop through a water purge line 312, as necessary, to a wateroutfall (not illustrated) with a controller 314. The pump(s) 310 supplythe force used to pass the cooled water therethrough to any and allwater users.

The water supplied to the safety shower water storage tank 290 iscontrolled by a water level control 315, which device maintains thewater level within the tank 290 at a suitable water level. Excess waterfrom the safety shower water storage tank passes therefrom through thewater line 291 and into the filter and water storage tank assembly 294of the pelletizer water distribution loop 292, where the water ishandled as described above. All water supplied to the pelletizer waterdistribution loop 292 and the cooling tower water loop 308 is suppliedfrom a suitable water supply W (potable water), as described above. Thisincludes all water added to each system for all water lost through thedownstream users 311 and the evaporation of water in thecutter/pelletizer station 300, as well as in the cooling tower 304.

Accordingly, the integrated plant water distribution system of thisinvention includes in a first embodiment a safety shower water storagetank in fluid communication with, and supplied by water from the watersource, a first water distribution loop in fluid communication with thesafety shower water storage tank and being supplied with watertherefrom, a second water distribution loop in fluid communication withthe first water distribution loop, and a control valve or valves forselectively drawing water from the first water distribution loop tosupply water to the second water distribution loop. Aspects of thissystem include the safety shower water storage tank being in fluidcommunication with a separate safety shower and eye wash system; a waterpipeline extending in sealed fluid communication from the safety showerwater storage tank to the first water distribution loop, wherein thefirst water distribution loop is supplied with water from the safetyshower water storage tank as the water overflows therefrom and is passedinto the first water loop. The first water distribution loop comprises apelletizer water loop constructed and arranged to supply water to apelletizing station used to pelletize a melted plastic polymer; a filterand water storage tank; a pump constructed and arranged to pump thewater from the water storage tank through the first water distributionloop; a heat exchanger; a filter; and a chemical additive station. Theheat exchanger is positioned downstream of the pump, the filter ispositioned downstream of the heat exchanger, the chemical additivestation is positioned downstream of the filter, the pelletizing stationis positioned downstream of the chemical additive station, and thefilter and water storage tank is downstream of the pelletizing station.

Additional aspects of the integrated plant water distribution systeminclude a water level control in fluid communication with the filter andwater storage tank, and a control valve intermediate and in fluidcommunication with each of the water level control and the safety showerwater storage tank. The water level control is constructed and arrangedto selectively add make-up water to the filter and water storage tankdirectly from the water source. The water level control is alsoconstructed and arranged to selectively control the supply of water tothe safety shower water storage tank to maintain the water level thereinat a predetermined water level.

The second water distribution loop comprises a cooling tower water loopwhich includes a cooling tower, a pump constructed and arranged to pumpthe water from the cooling tower through the second water distributionloop, and at least one cooling tower water user. The cooling towerfurther comprises a water collection basin formed as a part thereof forcollecting the water passed therethrough. The pump of the cooling towerwater loop is positioned downstream of the water collection basin, andthe at least one cooling tower water user is positioned downstream ofthe pump and upstream of the cooling tower. The second waterdistribution loop further comprises a purge line in fluid communicationtherewith, and a control valve in fluid communication with the purgeline for selectively passing water from the second water distributionloop. A second water pipeline extends in sealed fluid communication fromthe first water distribution loop to the second water distribution loopfor providing water thereto.

One aspect of the means for selectively drawing water from the firstwater distribution loop to the second water distribution loop comprisesa second pump in fluid communication with the second water pipeline,adapted to draw water from the first water distribution loop to thesecond water distribution loop therethrough. An additional aspect of themeans for selectively drawing water is a water level control in fluidcommunication with the cooling tower water collection basin, and acontrol valve intermediate and in fluid communication with each of thesecond pump and the cooling tower water collection basin. The waterlevel control for the cooling tower basin is constructed and arranged toselectively add make-up water to the cooling tower water collectionbasin from the second water pipeline, and is also constructed andarranged to establish a minimum water flow setting that will ensure thata satisfactory amount of water is always provided for the minimumrequired cooling flow of the second pump.

Another aspect of this invention is thus the method of distributingwater through an integrated plant water distribution system, the aspectsof the method including supplying water to a safety shower water storagetank, passing the water from the safety shower water storage tank intothe first water distribution loop, and selectively passing water fromthe first water distribution loop to the second water distribution loop.The method features the additional aspects of selectively adding waterto the first water distribution loop directly from the water source;passing the water in the first water distribution loop through themolten polymer pelletizing station; passing the water in the secondwater distribution loop through the water cooling tower; selectivelypassing water from the second water distribution loop through the waterpurge line in sealed fluid communication with the second loop; andselectively passing water from the first water distribution loop intothe cooling tower water collection basin forming a part of the secondwater distribution loop.

A preferred embodiment of an integrated vacuum system for use with thedescribed process/process plant is illustrated in FIG. 23. By using theintegrated vacuum system illustrated, the number of EG jets may bereduced, the chilled water system may be minimized, if not eliminated insome instances, and the number of components required for obtaining twostages of vacuum in the last polycondensation reactor is also minimized.

As illustrated in FIGS. 17 a and 17 b, respectively, polycondensationnormally has three stages of vacuum. Here the unique design of thisinvention integrates these last two stages of vacuum, the mediumpressure and the low pressure vacuum stages. The third vacuum stagecannot be integrated because the pressure in this stage is too high andwould not otherwise allow the EG vapor jet to have the properdifferential pressure for operation. Putting a valve in the vapor linehas led to plugging problems and is not a reliable solution.Nevertheless, two stages of vacuum can be effectively coupled.

Referring now to FIG. 23, a suitable and otherwise conventional vacuumpump 320 pulls a vacuum on an interstage condenser 321 used to condensecomponents such as EG and other condensables. A first EG vapor jet 322is installed between a spray condenser 324 and the interstage condenser,and which vapor jet will usually have a compression ratio of between 6to 8. The liquid discharge of the interstage condenser goes to a liquidseal vessel 325, also referred to as an immersion vessel. The dischargefrom the vacuum pump, as well as the liquid discharge from the spraycondenser can also be passed on to this seal vessel, or to any othertype of desired vessel. The liquid from the immersion vessel is thenpumped through a filter 326, a cooler 328, and either (a) returned tointerstage condenser 321 or spray condensor 324, or (b) is dischargedfrom this system at line 331 to, for example, the water column (notshown). Depending on the product being processed, the temperature of thesystem should be increased or decreased to control the vacuum as well asto control the buildup of low and intermediate boiling components, asknown.

The vacuum pump of the integrated vacuum system of this invention pullsthe vacuum from the polycondensation medium pressure vacuum stage orzone P2 into a top portion or region of the spray condenser through aline 244, as schematically illustrated. This medium pressurevacuum/vapor stream from the top of the final polycondensation reactoris connected to the spray condenser below the liquid cooling nozzles(not illustrated) within the top zone of the condenser. As shown, thevacuum connection extending from the spray condenser to the first EG jetis also at the top of the spray condenser, which allows thepolycondensation vapors to be condensed before going to the EG jet. Thishas the desirable effect of increasing the capability of the jet.

The polycondensation low pressure vacuum stage or zone P3 of the finalpolycondensation reactor is connected by a line 245 to a second EG jet330, and extends from there to a bottom portion or region of the spraycondenser. The vapors from this second EG jet thus enter the spraycondenser 324 at a point below the bottom liquid cooling nozzles (notillustrated) thereof. This allows the polycondensation vapors from thesecond EG jet, and the low polycondensation pressure vacuum from thebottom of the final reactor to condense without otherwise impairing ordiminishing the vacuum of the top of the polycondensation reactor.

Still referring to FIG. 23, the integrated vacuum system of theinvention also includes the necessary components for drawing a vacuumthrough the polycondensation high pressure vacuum stage or zone P1 usingthe vacuum pump 320. Accordingly, the high pressure vacuum zone is pipedinto a condenser 335 through a vacuum line 243. The vapors from the highpressure stage are cooled in the condenser 335, in known fashion. Theliquid/liquid condensate collected within the condenser is passed into asecond seal vessel 336 in fluid communication with the condenser.

This second seal vessel is in fluid communication with a pump 337 whichdraws the liquid/liquid condensate therefrom and passes it through adownstream filter 339. Thereafter, the liquid is chilled within achiller 340 in fluid communication with the filter, and the liquidpassed back into the condenser 335 for re-use, or passed to other userswithin the plant, as desired. A vacuum line 334 extends from the top ofthe condenser 335, and is in fluid communication with the vacuum pump320 through a control valve 343.

This design therefore eliminates one EG jet train, one spray condenserand pumping system, and only has two total EG jets rather than three pertrain. By putting all of the seal legs for the medium and low pressurevacuum zones to the same seal vessel, the number of seal vessels hasalso been cut to less than half. For example a dual system would havefive seal tanks, whereas a single system would normally have three sealtanks. This construction thus eliminates unnecessary equipment,instruments, and also reduces energy consumption otherwise needed tooperate a larger vacuum system.

As described, therefore, the integrated vacuum system of the inventionincludes a spray condenser in fluid communication with each of themedium and low pressure vacuum zones, respectively, of thepolycondensation reactor, an interstage condenser in fluid communicationwith the spray condenser; and a vacuum pump in fluid communication withthe interstage condenser. Additional aspect of the system include a sealvessel in fluid communication with each of the spray condenser, theinterstage condenser, and the vacuum pump, respectively; and a liquiddistribution system constructed and arranged to collect, filter, chill,and distribute liquid from the spray condenser and the interstagecondenser, respectively, to each of the spray condenser and theinterstage condenser, respectively. Other aspects includes the liquiddistribution system being constructed and arranged to collect liquidfrom the vacuum pump; the liquid distribution system being comprised ofa single seal vessel constructed and arranged to collect liquid fromeach of the spray condenser and the interstage condenser, respectively;and a control valve in fluid communication with the liquid distributionsystem and being constructed and arranged to selectively pass thechilled liquid to other users thereof, as desired.

Still other aspects of the system include the fluid from the lowpressure vacuum zone entering a bottom portion of the spray condenser,and the fluid from the medium pressure vacuum zone entering a spaced topportion of the spray condenser; a second spray condenser in fluidcommunication with the high pressure vacuum zone of the polycondensationreactor, the second spray condenser also being in fluid communicationwith the vacuum pump; a control valve disposed intermediate of and influid communication with each the second spray condenser and the vacuumpump; and a second liquid distribution system constructed and arrangedto collect, filter, chill, and distribute liquid passed from the secondspray condenser to at least the second spray condenser.

Yet another aspect of the integrated vacuum system of the inventionincludes a spray condenser in fluid communication with each of themedium and low pressure vacuum zones, respectively, of thepolycondensation reactor, a first EG jet in fluid communication with)the spray condenser, an interstage condenser in fluid communication withthe first EG jet, a vacuum pump in fluid communication with theinterstage condenser, and a second EG jet in fluid communication withthe low pressure vacuum zone and the spray condenser, respectively.Additional aspect of this embodiment of the invention include the fluidfrom the low pressure vacuum zone entering a bottom portion of the spraycondenser, and the fluid from the medium pressure vacuum zone entering aspaced top portion of the spray condenser; the first EG jet extendingfrom the top portion of the spray condenser; the second EG jet being influid communication with the low pressure vacuum zone and the bottomportion of the spray condenser; and a seal vessel in fluid communicationwith the spray condenser, the interstage condenser, and the vacuum pump,respectively, the seal vessel being constructed and arranged to collectliquid and liquid condensate therein. More aspects include a pump influid communication with the seal vessel for pumping the collectedliquid therefrom; a filter in fluid communication with the pump; achiller in fluid communication with the filter and being constructed andarranged to chill the liquid passed therethrough, the chiller being influid communication with each of the spray condenser and the interstagecondenser, respectively, and wherein the liquid chilled by the chilleris passed to the spray condenser and the interstage condenser,respectively; a control valve in fluid communication with the chillerand being constructed and arranged to selectively pass chilled liquid toother users thereof, as desired; a liquid collection and chilling systemconstructed and arranged to collect, filter, and chill liquid and liquidcondensate from the spray condenser, the interstage condenser, and thevacuum pump, respectively, and to redistribute the chilled liquid to thespray condenser and the interstage condenser, respectively.

The method of collecting fluid from the final polycondensation reactortherefore includes passing the fluid from at least the medium pressurepolycondensation vacuum zone and the low pressure polycondensationvacuum zone of the reactor into a single spray condenser in sealed fluidcommunication with each of the medium and low pressure vacuum zones,respectively, and drawing the fluid through an interstage condenser influid communication with the spray condenser with a vacuum pump in fluidcommunication with the interstage condenser. Additional aspect of themethod include passing the fluid from the low pressure polycondensationvacuum zone into a bottom portion of the spray condenser, and passingthe fluid of the medium pressure polycondensation vacuum zone into aspaced top portion of the spray condenser; passing the fluid from thetop portion of the spray condenser to the interstage condenser; passingthe fluid from the top portion of the spray condenser through a first EGjet in fluid communication with the spray condenser and the interstagecondenser; passing the fluid from the low pressure polycondensationvacuum zone through a second EG jet in fluid communication with the lowpressure polycondensation vacuum zone and the spray condenser,respectively; collecting liquid and liquid condensate from the spraycondenser and the interstage condenser in a seal vessel in fluidcommunication with each of the spray condenser and the interstagecondenser; filtering and chilling the liquid collected in the sealvessel, and passing the chilled liquid back to the spray condenser andthe interstage condenser, respectively; selectively passing at least aportion of the chilled liquid through at least one control valve influid communication therewith for use elsewhere, as desired; and passingthe fluid from the high pressure vacuum zone into a second spraycondenser in sealed fluid communication with the vacuum pump.

Adsorber System

In some embodiments, it may be desirable to replace the distillationcolumns with adsorbers. The adsorbers can use hot, inert gas fordesorption. Inert gas is any gas, which does not react with reactantsunder the conditions there present. Hot gas desorption produces glycolswith very low concentrations of water, which will improve the esterexchange or esterification conversion. In one aspect, at least onereactant is a diol compound, and wherein at least a portion of the diolcompound is removed from the process as a vapor, a liquid, or as both avapor and a liquid, and is subjected to an adsorption system toselectively recover the diol compound.

As shown in FIG. 19, the fluids from the process are fed to the firstadsorber 182. The process fluids sent to the first adsorber 182typically comprise vapors, liquids or a mixture thereof. This processfluid normally comes from a vapor stream off of the esterificationprocess, and the liquids come from the polycondensation and otherstreams, such as pump purges, pump seals, vacuum pumps, evaporatorpurges, intercondensers, etc. The process fluid stream continues to thesecond adsorber until a component that is desired for recovery breaksthrough the bed. All previous process vapor fluids leaving the adsorberare sent to the HTM furnace for incineration via line 184. At thispoint, the bed is saturated.

The use of adsorption reduces columns, equipment, tanks, agitators,pumps, etc. and replaces them in one embodiment, with a few simple largepipes or tanks, a compressor, and two heat exchangers. Adsorbtion savesenergy since no reflex is required like a distillation column, whichtypically has a reflux rate equal to the product draw-off rate. Anotheradvantage of absorption over distillation is that the diol will be morepure, which leads to less by-product in the product, such as lowered DEGand less coloration. Also, the by-product is reduced in the esterexchange or esterification reactor, such as water in the esterificationreactor. Water can have a significant impact on the reactor, and so, theesterificiation reactors can be smaller.

Process fluids enter adsorber bed 181 as stream 189 and exits in stream190. Stream 190 has a continuous monitoring instrument (such as an FTIR(Fourier Transform Infrared Analysis), but a single wavelength would beappropriate with experience, and the switching could be done with atimer after experience, and monitoring can be accomplished with manualgrab samples) that indicates when a component to be saved is exiting thebed. Until a desired component exits, all other components are sent viastream 190 to stream 184. Stream 184 goes to a thermal destructiondevice such as the Heat Transfer media furnace, a thermal oxidizer, acatalytic oxidizer, etc. Once bed 181 is loaded and a desired componentis exiting stream 190, the process fluids are sent into the nextabsorber bed.

In order to use the same drawing, bed 181 is now shown as the partiallyloaded bed that is being loaded via stream 189 from the reactors. Bed182 is the fully loaded bed described in the preceding paragraph. Bed183 is a fully desorbed bed. Bed 181 is being loaded as described in thefirst paragraph. Bed 182 has a hot stream of inert gas, such asnitrogen, carbon dioxide, argon, etc. supplied to it via stream 191coming from heat exchanger 188 which is heating the stream. Anyconvenient source of heat may be used such as steam, electricity, hotgas or vapor, hot liquids such as heat transfer, media, etc. Heat mayalso be exchanged between condenser streams 187, 191, 192, 193 andstream 199. Conventional air to air heat exchangers as wells as solidbed exchangers may be used. The motive force for the inert gas streamcomes from compressor or blower 186 although an eductor device may beused with inert makeup stream 197. The pressure on the inlet ofcomponent 186 is maintained by the addition of inert 197 andrecirculation stream 195.

The hot inert gas coming into bed 182 desorbs the components from thebed. Alternately, steam or other hot condensable vapor may be used, butthis detracts from the purity of the exiting stream and also requiresadditional separation equipment for the stream. Those skilled in the artwill control the flow and temperature of stream 191 to accurately desorbbed 182 separating the desorbed components into high purity, discretepulses. These pulses in stream 192 are monitored by a similar deviceused in stream 190. When a non-desired component is removed from bed 182into stream 192, a 3-way valve or multiple 2-way valves are switched andstream 192 is sent via stream 198 to the thermal oxidation device viastream 184. Alternately, stream 192 could pass through a non-cooledcondenser 185 and proceed to stream 184 for thermal oxidation. When adesired component is removed from bed 182 into stream 192, the valvesare switched and stream 192 proceeds to stream 199 and into condenser185. Condenser 185 can be cooled with air, refrigerated water,refrigerated gas, by expansive cooling, or other appropriate means. Thecooled stream 199 will fall below the saturation temperature and thedesired component will condense from the stream as a liquid. The liquidin stream 187 is directed to the appropriate storage container for thatproduct. Once stream 192 contains a non-desired component again, thevalves are again switched so that stream 192 goes to the thermaloxidation device. This switching process between desired and non-desiredcomponents continues until bed 182 is totally desorbed. Bed 182 thengoes to standby.

Gas from condenser 185 in stream 193 will contain the desired componentto be recovered, but is below the saturation temperature of condenser185. So, stream 193 is sent to the fully desorbed bed 183. Bed 183adsorbs the desired components cleaning stream 193. Stream 193 exits bed183 as stream 194. Stream 194 is directed back to blower or compressor186 as stream 195. Stream 197 adds makeup inert gas to maintain aconstant inlet pressure to compressor 186.

Once bed 181 is saturated and bed 182 has been previously desorbed, thebed functions cycle. Bed 181 takes the place of bed 182 in the cycle.Bed 182 takes the place of bed 183. Bed 183 takes the place of Bed 181.During the second phase Bed 181 will be desorbed, Bed 182 will catch thedesired components from condenser 185. Bed 183 will be saturated withreactor vapors. Once bed 181 is desorbed and bed 183 is saturated, thenext phase will begin.

Further enhancements may be necessary based on system sizes and productsbeing produced. Multiple adsorber beds may be required for each functionas well as multiple cooler, compressors, heater, and heat exchangers.The stream 189 from the reactors may be cooled before entering bed 181to improve the adsorption capacity of the bed.

Elimination of Gear Pump(s)

Most polyester plants have a gear pump between the prepolymer reactorand the finisher reactor. The pump overcomes the pressure drop betweenthe two reactors since the pressure difference is not great enough toprovide the required flow. The pump is also used as a metering device toprovide a uniform flow to the finisher allowing stable operation. Someprocesses have been constructed with the prepolymer reactor at a higherelevation than the finisher to provide the necessary pressuredifference. These plants forego the uniform flow to the finisher.

The pipe reactor system does not require a pump in the polycondensationsystem since the design of the piping inherently provides the pressurerequired to move the material to the next section of the plant. Inaddition, the pipe reactor has no level or pressure control systems toprovide upsets to the system that would be dampened by the gear pump.The pipe reactor dampens inlet perturbations. Since the pipe systemprovides a uniform flow without additional dampening and provides thehead pressure necessary to provide the flow between reactor sections, itdoes not need a gear pump in the polycondensation section.

Combined Esterification Pipe Reactor and Polycondensation Pipe Reactor

The individual sections recited above regarding the processes andapparatuses for esterification and polycondensation apply to, and can beused in, the combination and retrofit embodiments recited below.

As shown in FIGS. 6, 17A, and 17B, the two main pipe reactor stages ofthe present invention can be combined into an integral unit. FIG. 17Ashows one embodiment of the present invention. The esterificationreactor and polycondensation reactor are both pipe reactors. Reactivematerial is stored and fed from tank 221. In a preferred embodiment, itis solid PTA feed directly to recirculation line 224. The reactivematerial proceeds to solid metering device 222 from tank 221, which ison weigh cells 223. The solid PTA enters the recirculation line 224where it is mixed with the reactive monomer from the esterificationreactor 227, which has been recycled through line 230. The mixtureenters the heat exchanger 226 where it is heated. The mixture is thenfed to pipe reactor 227. Part of the reaction mixture is recycled backto line 230 to the influent of pump 225. Additional liquid additives,such as reactants, can be fed through line 240 into preferably theinfluent of pump 225. The effluent of pump 225 is fed through a pressurereducing device 246 to facilitate the solid feeding of the PTA from tank221. The esterification reactor can be vented at lines 231 and 232. Thevapor is preferably sent to refining. FIG. 17B differs from FIG. 17A, inthat an additional vent line 229 is present. Vent line 229 in one aspectis located just prior to the recirculation tee as shown in FIG. 17B, to,in certain aspects, remove water from the process. The other portion ofthe reactive mixture flows through the additional pipe reactoresterification process 228. The effluent from the esterification processis then optionally mixed with additional liquid additives at 234, is fedthrough heat exchangers 233, and is then fed to the polycondensationreactors 235, 236, and 237. The effluent, or completed polyester orpolymer, is fed through gear pump 238 and exits the system at 239.Pressure, specifically vacuum, in PET and PETG processes can becontrolled using vent or vacuum headers 243, 244, and 245. The vent orvacuum headers 243-245 can be fed to an oxidizer, such as an HTMfurnace, an incinerator, or a thermal oxidizer. Pressure differentialbetween the esterification sections or zones (E1/E2) andpolycondensation sections or zones (P1/P2/P3) can be controlled using apressure differential device, such as a seal leg 247, and the pressurebetween each of the polycondensation stages 235, 236, and 237, can becontrolled using a pressure differential device, such as a seal leg ateach of 241 and 242. In an alternative embodiment, instead of therecycle influent coming from the esterification process, the recycleinfluent can come from the polycondensation process, for example, as aslip stream off of effluent 239 (not shown in figure). This can increasethe liquid polymer uniformity.

One skilled in the art will also appreciate that the reactors of thepresent invention can be used to construct new plants, as well as toenhance or improve existing plants or to increase capacity. The pipereactors can be used to replace or can be inserted within a section ormultiple sections of an existing plant that is causing a technical orcapacity limitation. In one aspect, an esterification, polycondensation,or both pipe reactor apparatus(es) is constructed and arranged to beplaced in fluid communication with a conventional reactor for making apolyester monomer or polymer. For example, FIG. 5 shows possibleconfigurations where the second esterification reactor 212 does not haveenough volume to feed the polycondensation reactor 213 at its fullcapacity. In this situation, a pipe reactor 214 may be added between thefirst and second esterification reactors (211 and 212 respectively). Ifadditional residence time is required in the first polycondensationreactor 213, the pipe reactor 215 can be installed above the top of thefirst polycondensation reactor. Similarly, jacketed pipe can be added toincrease disengagement surface area to reduce liquid entrainment. Vaporremoved from the system is withdrawn via lines 216 and 217. Additionalpipe could be added to increase the heat transfer area. These pipingmodifications can be installed with the plant running (the pipe can evenbe routed to an outside wall to have enough room for the installation)except for the two end tie-ins. Then during a short shutdown, thetie-ins can be made, effectively adding capacity or performanceenhancement. These pipe reactor retrofits can be in series or inparallel to the existing facility CSTR or other type conventionalreactor(s). When the pipe reactor retrofit is in parallel to theconventional reactor, each of the respective pipe reactor andconventional reactor can be selectively operated, such that either onlyone of the reactors is operating at one time, or both of the reactorscan be operated simultaneously.

Alternatively, the pipe reactor retrofit can replace the existingreactor(s). In one embodiment, there is provided a polyester productionsystem, comprising the pipe reactor of the present invention retrofittedto a conventional polyester process comprising a conventional polyesterreactor, wherein the conventional reactor has been disabled from theproduction system. In another aspect, there is provided a method ofretrofitting a pipe reactor to a conventional polyester processcomprising (a) retrofitting the pipe reactor of the present invention ina conventional polyester process comprising a conventional polyesterreactor; and (b) disabling the conventional reactor from the process. Asused herein, disabling with respect to the conventional process refersto preventing the fluid from flowing to the conventional process, by,for example, providing a valve upstream of the inlet and downstream ofthe outlet to the conventional reactor and valving the conventionalprocess off or disconnecting the inlet and outlet of the conventionalreactor from the process system.

In the processes and apparatuses described herein, there can be greaterthan one esterification stage or zone and/or greater than onepolycondensation stage or zone. These multiple reactors can be placed inseries or in parallel.

Previous sections described the parameters for designing the pipereactor systems of the present invention. For large plants, it may notbe possible to acquire large enough pipe diameter to construct thereactor and meet the parameters. For such plants, a plurality of pipereactors can be operated in parallel. Multiple parallel pipe reactorscan be installed and combined at various locations within or between thezones. To minimize cost, the initial starting section of the reactor canbe mixed before splitting. This will eliminate the purchase ofadditional feed systems. The vapor lines can all go to the same vacuumtrain. The polycondensation reactors can share the same vacuum andcondenser systems. Thus, the only additional equipment, and costincurred, is the additional piping required.

In another embodiment, one single pipe reactor produces the polyesterpolymer from initial pre-monomer reactants. In this pipe reactor,reactants to make the monomer are fed in at one end and polyesterpolymer product is output at the other end. This is especiallyapplicable for polyester processes that do not have separateesterification and polycondensation steps. In this embodiment, the aboveaspects with respect to the separate esterification and polycondensationreactors and processes are applicable to this single pipe reactorprocess, such as the use of a weir, vapor removal and liquiddisengagement, geometrical orientation of the pipe reactor, etc.

Accordingly, in one aspect, the pipe reactor divides into a plurality ofsubstantially parallel flow conduits extending between the inlet and theoutlet thereof, and wherein the reactant flowing through the pipereactor passes through one of the plurality of flow conduits whileflowing through the reactor. In another aspect, at least two separateesterification pipe reactors are provided, each of which produces thesame or a different polyester monomer, and wherein the fluid polyestermonomer exiting the respective esterification pipe reactors is directedinto the first end of the polycondensation pipe reactor. In anotheraspect, at least two separate polycondensation pipe reactors areprovided, each of which produces the same or a different polyesterpolymer, and wherein each fluid polyester monomer exiting the respectiveesterification pipe reactors is directed to the first end of at leastone of the respective polycondensation pipe reactors. In another aspect,the esterification pipe reactor comprises a plurality of esterificationreactors positioned in parallel to one another with a common inlet. Inanother aspect, the polycondensation pipe reactor comprises a pluralityof polycondensation reactors positioned in parallel to one another witha common first end. In this embodiment, a co-reactant can be added to atleast one of the plurality of polycondensation reactors but not to allof the polycondensation reactors to thereby produce at least twodifferent polyester products.

SOME EXPECTED ADVANTAGES OF THE PRESENT INVENTION

One benefit of the present invention is that the design allows thereactor to be constructed in areas that contain interferences. The pipecan be fabricated around columns, beams, other pipes, other reactors,distillation columns, etc.

Also, many embodiments of the present invention do not require pressureor level control. The pressure at the bottom of the esterification orester exchange reactor is controlled by the pressure losses due tofriction, the static head from the reactor liquid contents, and the backpressure on the vapor lines leaving the reactor. Since the goal is toreduce the pressure in the reactor in a prescribed pressure profile, thereactor piping is configured to produce the profile. This eliminates theneed for pressure control with valves. But it is possible to control thedistillation or vapor exhaust pressure and add this delta pressure tothe entire esterification or ester exchange reactor.

Nearly every aspect of the conventional polymerization train is greatlysimplified by the pipe reactor of the present invention. Theinstrumentation, valves and control loops required are greatly reduced,and pumps, reactor agitators, reactor screws, and associated sealsystems are eliminated. Except for a pump, if one is used for arecirculation group, the pipe reactor systems of the present inventionhave little or even no moving parts. The reduction and removal of thesecomponents from the plant greatly reduces the amount of computer andcontrol equipment required, capital costs, maintenance costs and utilityconsumption. The pipe reactor can be welded without gaskets, whichreduces emissions out of the reactor and air leakage into the reactor,thereby improving product quality. The substantial reductions inequipment and control systems also provide decreased operating costs.

The pipe reactors of the present invention can be constructed andinstalled in less time than reactor vessels. The piping can be shop orfield prefabricated. The pipe reactor sizes can be designed to allow thereactor sections to be shipped by standard trucks, shipping containers,lorries, etc. without obtaining costly and slow oversize or overweightshipping permits. The prefabrication allows modular plant designs wherethe piping can be constructed, pressure tested, and insulated in theshop, reducing field construction time and at a lower cost.

The liquid volume required for polyester pipe reactor design of theinvention is substantially less than a conventional polyester process.Additionally, the amount of particular by-products produced can begreatly reduced by utilizing a pipe reactor design of the instantinvention. In one aspect of the instant invention, wherein PET isproduced, the instant invention can achieve a level of DEG impurity inthe final produce of less than 1.2 weight percent, in another aspectless than or equal to 1.0 weight percent, in another aspect 0.74-1.0weight percent. This is to be contrasted with a typical conventionalprocess for making PET, wherein the typical range for DEG impurity levelis from 1.2 weight percent to 2.0 weight percent. In fact, this reducedamount of DEG impurity in the final product can be achievedsimultaneously with a drastic liquid volume reduction achievable withthe polyester pipe reactor design of the instant invention.

EXAMPLES

The following examples are put forth so as to provide those of ordinaryskill in the art with a complete disclosure and description of how thecompounds, compositions, articles, devices and/or methods claimed hereinare made and evaluated, and are intended to be purely exemplary of theinvention and are not intended to limit the scope of what the inventorsregard as their invention. Efforts have been made to ensure accuracywith respect to numbers (e.g., amounts, temperature, etc.), but someerrors and deviations should be accounted for. Unless indicatedotherwise, parts are parts by weight, temperature is in ° C. or is atambient temperature, and pressure is at or near atmospheric.

ASPEN modeling was used for the data below. Where ASPEN modeling isreferenced in the examples, it is ASPEN 10.2, service patch 1, withPolymers Plus, and ASPEN's PET Technology, except as indicated below.The esterification reactor is modeled as a series of 5 CSTR reactormodels followed by a plug flow model.

Example 1

Using ASPEN modeling, exemplary pipe lengths and heat exchange areaswere calculated for a pipe reactor system for each of PET and PETG. Theresults are shown in Table 1 below.

TABLE 1 Esterification Polycondensation Pipe Diameter in 14 12 14 16 PETPlant Pipe ft 733 1775 1905 Length Stage 1 Stage 2 PET Plant Heat ft²2200 2000 Exchanger Area PETG Plant ft 79 75 255 680 Pipe Length Stage 1Stage 2 Stage 3 PETG Plant ft² 2200 1900 Heat Exchanger Area

Example 2

The liquid volume required for a polyester pipe reactor design issubstantially less than a conventional polyester process. For example,ASPEN modeling was run to compare to a 300 million pounds per year PETbottle plant. The results are set forth in Table 2 below.

TABLE 2 Esterification Standard Plant 100 m³ Pipe Reactor 8.4 m³ %Reduction 92% Polycondensation Standard Plant 35.6 m³ Pipe Reactor 14.2m³ % Reduction 60% Total Plant Standard 135.6 m³ Pipe Reactor 22.6 m³ %Reduction 83%

Examples 3-7

Various ASPEN modeling was run to determine operating conditions andperformance results for various polyesters of the invention. Themodeling was based upon an apparatus of the invention of either FIG. 17a or 17 b as noted in the Tables below. The inherent viscosity (I.V.) ismeasured by dissolving of 0.25 g of polymer in 50 mL in the solvent,which consists of 60% phenol and 40% 1,1,2,2-tetracholorethane byweight. The measurement is made at 25 deg C. using either a ViscotekDifferential or Modified Differential Viscometer using ASTM D 5225,“Standard Test Method for Making Solution Viscosity of Polymers with aDifferent Viscometer.” The results for Examples 3-7 are set forth belowin Tables 3-7, respectively.

TABLE 3 HOMO PET-Bottle Polymer Recycle Rate 5 parts monomer to 1 partPTA by weight Production Rate 300 million pounds/year EG to PTA feedmole ratio 1.6 Poly- Poly- Poly- conden- conden- conden- Reactor (Seesation sation sation FIG. 17A) Esterification zone 1 zone 2 zone 3Temperature (C.) 296 296 296 296 Pressure (psig) 10 down to 2 Pressure(torr abs) 61 10 0.5 Liquid volume (m3)   16.2 3.7 3.3 9.9 E1 P1 P2 P312 in pipe (ft) 632 253 14 in pipe (ft) 935 830 16 in pipe (ft) 1875heat exchanger (ft2) 2200  2200 Finished Product IV 0.60 dL/g DEG 0.78wt % Acid Ends 33 mole equivalent per 1 million grams Vinyl Ends 1.5mole equivalent per 1 million grams

TABLE 4 PETG Copolyester (20.5 wt % CHDM) Recycle Rate 10 parts monomerto 1 part PTA by weight Production Rate 95 million pounds/year EG to PTAfeed mole ratio 3.5 Poly- Poly- Poly- conden- conden- conden- Reactor(See sation sation sation FIG. 17A) Esterification zone 1 zone 2 zone 3Temperature (C.) 255 255 275 275 Pressure (psig) 47 down to 25 Pressure(torr abs) 120 5 0.5 Liquid volume (m3)   4.6 4.0 5.0 3.2 E1 P1 P2 P3 12in pipe (ft) 213 85 14 in pipe (ft) 201 254 16 in pipe (ft) 680 heatexchanger (ft2) 2000  2000 Finished Product: IV 0.75 dL/g

TABLE 5 HOMO PET-Bottle Polymer Recycle Rate 5 parts monomer to 1 partPTA by weight Production Rate 300 million pounds/year EG to PTA feedmole ratio 1.6 Poly- Poly- Poly- conden- conden- conden- Reactor (Seesation sation sation FIG. 17B) Esterification zone 1 zone 2 zone 3Temperature (C.) 296 296 296 296 Pressure (psig) 10 down to 2 Pressure(torr abs) 11 10 0.5 Liquid volume (m3)   8.4 1.7 27 9.8 E1 E2 P1 P2 P312 in pipe (ft) 318 127 14 in pipe (ft) 630 1005 16 in pipe (ft) 1875heat exchanger (ft2) 2000  2000 Finished Product: IV 0.60 dL/g DEG 0.94wt % Acid Ends 35 mole equivalent per 1 million grams Vinyl Ends 1.5mole equivalent per 1 million grams

TABLE 6 HOMO PET-Fiber Polymer Recycle Rate 5 parts monomer to 1 partPTA by weight Production Rate 300 million pounds/year EG to PTA feedmole ratio 1.6 Poly- Poly- Poly- conden- conden- conden- Reactor (Seesation sation sation FIG. 17B) Esterification zone 1 zone 2 zone 3Temperature (C.) 296 296 296 296 Pressure (psig) 10 down to 2 Pressure(torr abs) 11 10 0.5 Liquid volume (m3)   8.4 1.9 2.4 7.7 E1 E2 P1 P2 P312 in pipe (ft) 313 125 14 in pipe (ft) 704 893 16 in pipe (ft) 1473heat exchanger (ft2) 2000  2000 Finished Product: IV 0.55 dL/g DEG 0.94wt %

TABLE 7 PETG Copolyester (20.5 wt % CHDM) Recycle Rate 10 parts monomerto 1 part PTA by weight Production Rate 95 million pounds/year EG to PTAfeed mole ratio 3.5 Poly- Poly- Poly- conden- conden- conden- Reactor(See sation sation sation FIG. 17B) Esterification zone 1 zone 2 zone 3Temperature (C.) 255 255 275 275 Pressure (psig) 47 down to 25 Pressure(torr abs) 120 5 0.5 Liquid volume (m3)   2.3 2.5 5.0 3.2 E1 P1 P2 P3 12in pipe (ft) 106 43 14 in pipe (ft) 125 254 16 in pipe (ft) 680 heatexchanger (ft2) 2000  2000 IV 0.75 dL/g

In comparing Table 3 to Table 5, the following can be observed. With novapor disengagement in the verification process (Table 3 data), the DEGby-product is 0.78 weight percent, versus Table 5 data, which does havethe vapor disengagement in the esterification section of the reactionand produces a DEG by-product of 0.94 weight percent. However, with thevapor disengagement in esterification system, the liquid volume isreduced from 16.2 m³ down to 8.4 m³ (compare Table 5 with Table 3).Removing water during the esterification process, as shown in Table 5,drives the reaction to produce monomer but also drives the reaction toproduce additional DEG. However, the liquid volume of the reactor isdrastically reduced. In this case, for PET, the volume reductionsupercedes the increased rate of DEG production and provides a finalproduct with slightly higher DEG but with the liquid volume of thereactor reduced by almost 50%. This would be expected to result in asubstantial capital investment savings and operating expense savings forPET production.

Additionally, both Tables 3 and 5 show that the DEG by-product of 0.78weight percent and 0.94 weight percent respectively, are lower than thattypically found using a conventional CSTR process, which is from 1.2 to2.0 weight percent.

Additionally, as noted in Tables 3-6, the reactors are run hotter thanconventional CSTR reactors. In the embodiment shown in Tables 3-6, thereactors were run at 296° C., as contrasted to conventional CSTRreactors, which are typically run at about 262° C. Surprisingly, thepipe reactors able to be run hotter than a CSTR without the negativeside effects of increased DEG production, as shown in the final productdata in Tables 3-6. It may be theorized that this is due to the smallerresidence time in the pipe reactor as compared to a CSTR reactor. Thehotter reaction temperature also enhances the process by allowing theincreased vaporization of water off of and out of the process.

Example 8 Lab-Model Comparison

Lab Scale Reactor

A lab scale esterification pipe reactor was built to demonstrate suchesterification of PTA and EG in a laboratory setting. The lab unitconsisted of a pipe reactor made of 664.75 inches of 0.5″ 18 BWGstainless tubing heated by electric tracing, a 1200 ml receiver withagitator for receiving the output of the pipe reactor and acting as adisengagement zone to allow the removal of vapors, a recirculatingmonomer gear pump which pumps liquid oligomer from the receiver backinto the inlet of the pipe reactor, and a PTA/EG paste feed system whichfeed raw materials into the recirculating loop. The reactor was startedby charging a PTA based CHDM modified (2.5 weight percent) oligomer ofapproximately 96% conversion into the receiver (C-01) and filling thepipe reactor with this oligomer in recirculating mode. Afterrecirculating the oligomer at temperature, a PTA/EG paste feed wasintroduced into the recirculating flow. After the reactor reached steadystate, samples were taken from the C-01 receiver at a rate equal to theproduct generation rate.

These samples were analyzed for percent conversion by proton NMRanalysis to determine the extent of reaction that took place in the pipereactor. Percent conversion based on Esters was determined by Proton NMRusing a Trifluoroacetic Anhydride Method:

Ten mg of the sample to be analyzed is dissolved in 1 ml of a solventmixture of chloroform-d with 0.05% Tetramethylsilane(TMS)/trifluoroacetic acid-d/trifluoroacetic anhydride in a 72/22/8volume ratio. The mixture is heated to 50° C. and stirred as needed tocompletely dissolve the sample to be analyzed.

The appropriate amount of the sample solution is transferred into a 5 mmNMR tube and the tube is capped. The proton NMR signal is recorded usingan average of 64 signals collections. The NMR signal using a 600 MHz NMRand a NMR pulse sequence is collected which gives quantitative protonNMR signals and also decouples the carbon 13 NMR frequencies. The NMRspectrum is analyzed by measuring the correct areas and calculating thepercent conversion of acid groups to ester groups by the areas andcalculations below:

Areas between the following chemical shift points referenced to TMS aremeasured, and percent conversion calculated using the formula.

-   Area A=7.92 ppm to 8.47 ppm-   Area B=5.01 ppm to a valley between 4.82 and 4.77 ppm-   Area C=4.82 ppm to a valley between 4.74 and 4.69 ppm-   Area D=A valley between 4.28 ppm and 4.18 ppm to a valley between    4.10 and 4.16 ppm-   Area E=A valley between 4.10 ppm and 4.16 ppm to a valley between    4.0 and 4.08 ppm-   Area F=8.6 ppm to 8.9 ppm-   Area G=7.55 ppm to 7.8 ppm    Percent Conversion=100*(B+(0.5*C)+D+(0.5*E))/(A+F+G)

The samples were also analyzed by gas chromatograph for percent DEG bymass to determine the rate of the side reaction. The effect of residencetime and recirculation ratio was seen by varying the feed rate of thepaste

Results from laboratory runs can be seen in Table 8 below.

TABLE 8 Recirc Paste Feed Feed Temp Pressure Rate Rate Mole RatioMeasured Measured Experiment (° C.) (psig) (lbs/hr) (lbs/hr) (EG/PTA) %Conversion weight % DEG 1 285 0 67 1 1.8 94.2% 1.1% 2 285 0 67 1 1.893.7% 1.1% 3 285 0 67 1 1.8 92.5% 1.4% 4 285 0 67 1.5 1.8 92.7% 1.0% 5285 0 67 2 1.8 90.9% 0.6% 6 285 0 67 2.5 1.8 87.2% 0.7% 7 285 0 67 3 1.864.2% 0.2% 8 285 0 67 3.5 1.8 67.1% 0.6% 9 285 0 67 4 1.8 51.9% 0.3% 10285 0 67 3.5 1.8 77.4% 0.3%Model Comparison

An ASPEN model was used to simulate the lab apparatus previouslydescribed in this example. In this case, ASPEN 11.1 with Polymers Plus,and ASPEN's PET Technology was used for the modeling with a modelconfiguration similar to the one described for examples 1-7. Neithermodel configuration nor software were significantly different from thatused in Examples 1-7. In order to correctly simulate the dissolution ofPTA into the oligomer at different conditions in the lab, it wassometimes necessary to add dissolution kinetics to the model. Table 9shows three comparisons of lab runs with the model without dissolutionkinetics included; this model was found to be of reasonable accuracywhen the experimental conditions resulted in completely dissolved PTA asin these runs. Table 9 also shows two examples of comparisons of labruns with the model including the dissolution kinetics; this modelincluding the dissolution kinetics closely matches the measuredconversion when free PTA is present at the end of the lab scale pipereactor as in these runs. Conversion is defined in this context as thepercentage of reactive (acid if use PTA as here) end groups in theliquid phase that are esterified as measured at the outlet of reactor.

TABLE 9 Completely Dissolved PTA - No Dissolution Kinetics in ModelPaste Paste Monomer Mole Weight % Model Feed Circulation Temp. RatioUnreacted Predicted Measured (g/min) (g/min) (° C.) (EG/PTA) PTA (%Conversion) (% Conversion) 8 507 263.2 1.8 0.00 97.053 95.170 8 507253.9 1.8 0.00 96.645 93.750 15 507 265.5 1.8 0.00 96.269 91.630 PTA NotCompletely Dissolved/Dissolution Kinetics in Model Paste Paste MonomerMole Weight % Model Feed Circulation Temp. Ratio Unreacted predictedMeasured (g/min) (g/min) (° C.) (EG/PTA) PTA (% Conversion) (%Conversion) 19 507 261.5 1.8 2.93 90.935 86.500 15 507 261.5 1.8 3.3490.228 85.490

Throughout this application, various publications are referenced. Thedisclosures of these publications in their entireties are herebyincorporated by reference into this application in order to more fullydescribe the state of the art to which this invention pertains.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the scope or spirit of the invention. Otherembodiments of the invention will be apparent to those skilled in theart from consideration of the specification and practice of theinvention disclosed herein. It is intended that the specification andexamples be considered as exemplary only, with a true scope and spiritof the invention being indicated by the following claims.

1. A method of producing an oligomer and/or polymer having aterephthalate moiety, said method comprising the steps of: (a)generating a gaseous fluid from a liquid fluid to thereby provide atwo-phase fluid stream, wherein said generating is at least partlyaccomplished by heating said liquid fluid and/or by subjecting at leasta portion of said liquid fluid to a chemical reaction, wherein saidheating vaporizes at least a portion of said liquid fluid to therebyform a vaporized fluid, wherein said chemical reaction forms a gaseousby-product, wherein said gaseous fluid comprises at least a portion ofsaid vaporized fluid and/or at least a portion of said gaseousby-product; (b) flowing at least a portion of the two-phase fluid streamthrough a pipe reactor, wherein the pipe reactor comprises at least onehorizontally-elongated pipe segment, wherein said two-phase fluid streamflows in a stratified flow regime through at least a portion of saidhorizontally-elongated pipe segment, wherein said stratified flow regimeincludes having at least a portion of said gaseous fluid flow above atleast a portion of said liquid fluid; and (c) separating at least aportion of the gaseous fluid from the liquid fluid to thereby provide aseparated gaseous fluid and a separated liquid proximate a locationwhere the liquid and gaseous fluids are in stratified flow, wherein saidseparating includes routing the separated gaseous fluid to a differentlocation than the separated liquid fluid.
 2. The method according toclaim 1 wherein said gaseous fluid generated in step (a) issubstantially the only gas-phase fluid present in the stratified flowregime.
 3. The method according to claim 1 wherein step (a) includesreacting at least a portion of the liquid fluid in the pipe reactor tothereby produce at least a portion of the gaseous fluid.
 4. The methodaccording to claim 3 wherein said reacting includes esterifying.
 5. Themethod according to claim 3 wherein said reacting includespolycondensing.
 6. The method according to claim 3 wherein said reactingincludes forming the oligomer and/or polymer in the liquid fluid.
 7. Themethod according to claim 6 wherein said oligomer and/or polymer is acondensation polymer.
 8. The method according to claim 6 wherein saidoligomer and/or polymer is a polyester.
 9. The method according to claim6 wherein said oligomer and/or polymer is PET.
 10. The method accordingto claim 1 wherein step (a) includes heating the liquid fluid to therebyvaporize a portion thereof.
 11. The method according to claim 1 whereinstep (c) includes venting said at least a portion of the gaseous fluidfrom the pipe reactor.
 12. The method according to claim 1 wherein step(c) includes reducing the flow velocity of the liquid and gaseous fluidsto thereby cause disengagement of the liquid and gaseous fluids.
 13. Themethod according to claim 1, further comprising the step of: (d)transporting the gaseous and liquid fluids upwardly in the pipe reactorby creating a pressure differential in the pipe reactor.
 14. The methodaccording to claim 1 wherein said pipe reactor has a generallyserpentine configuration.
 15. A method of producing a condensationpolymer, said method comprising the steps of: (a) condensing liquidmonomers and/or liquid oligomers in a pipe reactor to thereby produce agaseous condensation by-product and a liquid condensation mixturecomprising the condensation polymer, wherein said pipe reactor comprisesat least one horizontally-elongated pipe segment; and (b) flowing theliquid condensation mixture and the gaseous condensation by-productthrough at least a portion of the horizontally-elongated pipe segment,wherein at least a portion of said flowing is carried out in a flowregime selected from the group consisting of stratified flow, wavy flow,slug flow, plug flow, bubble flow, froth flow, and combinations thereof.16. The method according to claim 15 wherein said flow regime isstratified flow.
 17. The method according to claim 15, furthercomprising the step of: (c) disengaging at least a portion of thegaseous condensation by-product from the liquid condensation mixture.18. The method according to claim 17 wherein step (c) includes reducingthe flow velocity of the gaseous condensation by-product and the liquidcondensation mixture.
 19. The method according to claim 17, furthercomprising the step of: (d) removing the disengaged gaseous condensationby-product from the pipe reactor.
 20. The method according to claim 15wherein said condensation polymer is a polyester.
 21. The methodaccording to claim 15 wherein said condensation polymer is PET.
 22. Themethod according to claim 15, further comprising the step of: (e)forming the liquid monomers and/or the liquid oligomers in another pipereactor.
 23. The method according to claim 22 wherein said formingincludes esterifying.
 24. A method of producing an oligomer and/orpolymer, said method comprising the steps of: (a) esterifying a liquidreactant in a pipe reactor to thereby produce a gaseous reactionby-product and a liquid reaction mixture comprising an ester reactionproduct of said esterifying, wherein said pipe reactor comprises atleast one horizontally-elongated pipe segment; and (b) flowing theliquid reaction mixture and the gaseous reaction by-product through atleast a portion of the horizontally-elongated pipe segment, wherein atleast a portion of said flowing is carried out in a flow regime selectedfrom the group consisting of stratified flow, wavy flow, slug flow, plugflow, bubble flow, froth flow, and combinations thereof.
 25. The methodaccording to claim 24 wherein said flow regime is selected from thegroup consisting of bubble flow, froth flow, stratified flow, andcombinations thereof.
 26. The method according to claim 24 wherein saidflow regime is stratified flow.
 27. The method according to claim 24,further comprising the step of: (c) disengaging at least a portion ofthe gaseous reaction by-product from the liquid reaction mixture. 28.The method according to claim 27 wherein step (c) includes reducing theflow velocity of the gaseous reaction by-product and the liquid reactionmixture.
 29. The method according to claim 27, further comprising thestep of: (d) removing the disengaged gaseous reaction by-product fromthe pipe reactor.
 30. The method according to claim 24 wherein saidester reaction product comprises a terephthalate moiety.
 31. The methodaccording to claim 24, further comprising the step of: (e)polycondensing the ester reaction product in another pipe reactor tothereby form a condensation polymer.
 32. The method according to claim31 wherein said condensation polymer is PET.